While it looks like it is turned on in your screenshot there are two ways to check and change that.
1. the small gear symbol in the lower right corner will allow you to change this. If it only suggests to turn it off, that means it is turned on.
2. You can right click on the root of the browser and the menu will also alloww to tunrn it on/off. Again if it suggests you can turn it off it means you currntly have it turned on.
However, once you have recorded events in teh timeliine and you turn it off it converts all of the information into direct modeling features and you cannot get those back bt turning timeline recording back on. It will only record from that point on forward.
I just tried what I suggested above. You don't need to convert the T-Spline. You can just select "Modify->Fillet" and then select the edge you want to fillet.
Then you need to chenge the setting in the pop-up Window from"Constant radius" to "Variable Radius" and play around with that. Set it to "G2" as well.
Also, please accpept my apologies for my utter ignorance of kayaking, but what is the front and what is the back ?