This seems to be generally true, something in the way comedians balance internal vs. external perception seems to be different. This may have especially been true for Robin Williams, who it is said was “always on”. His act wasn’t so much an act but an amplified version of who he really was.
I remember a segment on an old 60 Minutes improvising with Jonathan Winters, who was his mentor, and friend. Of course it’s on Youtube and is still worth a look:
https://www.youtube.com/watch?v=iDJjq0Pd0RM
That was great. Thanks for posting it.