I look at the whole where to put my foot this way... First, because of unwanted slowdowns for various reasons, I keep my foot over the accelerator to lessen the impact of those events. second, and I think more applicable to help with the people who want to hover over the brake...
In an ICE car when you are driving, where is your foot when not on cruise control? It's on the accelerator...but no one complains about not being able to get to the brake in time...
Now for cruise control in an ICE, well really most any car...where is your foot? I'll say probably over/near the brake...but why? Because it is an easy way to stop the cruise control, AND it doesn't cause a big slowdown event at the time of disengagement...BUT you are probably going to be moving back to the accelerator pretty quickly to maintain speed.
If, given that in either an ICE or a Tesla, you keep your hands on the wheel, then disengaging TACC in a Tesla is an easy flick of the right stalk, and your foot being over the accelerator allows you to avoid a usually unnecessary abrupt regen induced slowdown. I would say that normally, needing to disengage any form of cruise control, there is no need to slow down abruptly.