That is a deep subject, that I am not going to buy in to it, other than to say, someone has to demo that it exists,
Direct Modelling suits specific purposes, as he mentioned,
Concepting and modelling on objects imported without history are a couple,
While he didn't say much, there are functions that are, or are not, available in both environments,
Turning off history is a one way street, you can't bring it back, without opening an old version and promoting it.
(he said, "We don't need it" for his demo, that was true) your confused, I won't do it.
I am a history modeller, I want to keep the timeline, and edit as I go, I am familiar with it,
you could get all the same results by editing the sketch / feature in the history version.
So even in these circumstances, why is it important to turn off history?
Some functionality changes in each area, he needs the DM functions.
My Opinion: His actions would break the timeline, so delete it before it breaks.
Might help.....