From: Diomidis Spinellis
I remember being told back in the 1980s that vi would
set the terminal
to "cooked mode" when vi was in "insert mode", so as to reduce
expensive
context switching for each character typed.
...
However, I can't find such evidence even as far back as BSD 1.
Maybe you're thinking of Multics Emacs, which had such a capability:
https://multicians.org/mepap.html
Noel