I agree that selecting an item from the menu that is already shown as the selection shouldn't change anything.
BUT the point I'm making is that the selected option doesn't give you what you want in the first place. SO I'm saying that there is no reason not to have 'new body' created when you select it. You are specifically telling the program to make a new body at that point. So in this case there is no need to keep the non functionality of the Default 'New Body' selection. Just give the new body as requested. I can't see this as causing some problem, and would be a big improvement.
So we narrowed the problem down to this. Using our analogy, with our restaurant menu. I want the choice on the cover or in the menu and when I do that I get it. You are saying if you pick what is on the cover you don't get it and if you pick the same thing from inside the menu you also get what you don't want because it's already on the cover.
I hope you are beginning to see the light here.
I put up an Idea to the 'idea station' as you suggested:
I received a few comments from other Fusion360 users:
1) "If it's an option, I'm for it"
2) "The option to turn this off is a good idea"
3) "My current project involves a bunch of lumber and I'm having the same problem (though not to the same extent I'm sure). I can't imagine that this is that hard to implement. This is one of the first frustrations I had using the program. Generally I want to create a new body rather than join (or cut). In fact, I'm having a hard time thinking of when I would have a bunch of joins to do repeatedly and the auto selection would actually help me out. Don't we usually construct things out of smaller pieces? I understand the purpose of this feature but it's really painful when you have a lot of extrusions to do and it chooses the wrong option every single time. "
4) "Seriously!!?? This is my biggest gripe when using Fusion 360. I also want to be able to set "New Body" as the default. PLEASE!!!!!"
5) "Hey Autodesk can you please make this an option. ...it's such a cumbersome thing to have to change from Cut to New Body each time I extrude.
I also have designs that have hundreds of components and the lag from Fusion to process the DEFAULT Cut each time is seriously frustrating.
Imagine each time you wanted to push the brake pedal your foot first had to touch the gas pedal...
Love the program but still find this to be the most cumbersome thing."
6) "agreed. As a new fusion user, this is something I intuitively expected. I searched 100% assuming there was a way to change the default operation. Mine shows "new body" as the operation until I extrude, then it automatically switches to "join". I have to finish the extrusion, and then switch back to "new body"
I do not have 25 years of experience with cad. Congrats to you. In that regard I have only the experience with Fusion360 and only within the modeling environment. I have never looked at the other stuff like CAM etc. because I do not require it. That being said, I have been given AutoDesk Elite status and all I know of Autodesk is one part of one program. Autodesk recognizes me as an expert in the modeling environment of Fusion360. I do not consider myself an expert as I do not know everything that an expert should know. I only need to know what I need to know to do the job.
Even though I can model relatively quickly in Fusion360, the two things that trip me up is:
1) AutoCut/AutoJoin
2) Double clicking while holding the shift. In many cases will zoom out to see the full model, that's a drag when you are zoomed way in on something and just want to rotate it. This also needs an option to turn that off in the prefs.
Those two changes alone would make for vastly improved user experience, and in no way have any effect on a user that doesn't want to choose that option!
Here's an example of my work:


I do not think users would get confused if they could turn off AutoCut/AutoJoin and all of a sudden they get what they want.
They do get confused however when it's unexpectedly changing to something else.
Think it through some more and don't let your 25 years of experience limit your thinking to 'it's always been that way'. There are a lot of new users yet to come with no experience who will be confused with this, and you are concerned the an experienced CAD user might get confused if they pick 'new body' from the drop down and get one?
"Oh I'm so confused?" I really don't think so.
I hope other people on the F360 team are seeing this beside you.
I'm glad you liked my story... just wanted to make it very clear what the problem is. I think you are close by now to understanding this. I have no problem understanding you and where you are with this, but I am trying my best to get a change made to the program and so far I do not feel the support from you to make that happen. Maybe someone there that agrees with me might be who I should be talking to. But thanks, I always find it amazing when people cannot understand something very simple. I could thicken the plot to make it clearer but if it ain't clear already then I need to be talking with someone who can understand this better than you. Components are great for a number of things but shouldn't have to used simply because you want to avoid a AutoCut/AutoJoin operation.
Imagine for moment a senario where you could turn off the Auto/Cut from the prefs in Fusion360 and the user has it turned off. Now the user goes to make an extrude and he sees that 'NewBody' is the title at the top of the menu. He makes the extrude. The extrude happens very quickly because it is not calculating a cut or join at this point.
That was so easy. If he wants to join, cut or intersect then he goes and chooses it from the menu...DONE!!! YESSS that's what I'm talking about.
This would not confuse anybody, so your argruement doesn't hold up at all. It would be the new expected behavior, giving the user what he ask for. What a novel idea!
BTW, I have made suggestions in the past for changes to Fusion360 that were eventually implemented, including having the option in the prefs to turn of AutoHide of Sketches.
I'm sure by now that the point I am making is clear. Even someone who has never used Fusion360 would understand such a well stated case.
Cheers