Why does “the velt” that generally follows Reb Moshe’s psakim disregard Reb Moshe when it comes to air conditioners on a Shabbos clock?
R’ Moshe’s talmidim might very well avoid use of timers on Shabbos.
Many people follow many of his psakim, but not necessarily all. This may very well be one of those psakim which most poskim of his time disagreed with, and therefore wasn’t widely accepted.