This question is illustrated by my personification of 3 microwave ovens:
Microwave 1 is rude. It beeps when time expires and keeps beeping even after I open the door. It also beeps to cancel settings if I open the door before it times out. It doesn't respect my need to discretely heat the last muffin. Busted!
Microwave 2 is reluctantly compliant. It beeps when time expires but will cancel the beep if I open the door before time expires. If I open the door at the correct picosecond, I can also avoid resetting the timer and avoid all beeping.
Microwave 3 is an indulging butler. He will beep only after several seconds beyond the time I entered to heat the muffin. I can imagine a conspiratorial wink as I open the door before the beep even starts.
I am sure this concept applies to other domains besides time. It is distinct from, but relates to "hover intent" or "Hysteresis". These terms refer to carefully timed closely coupled sequences, such as menu drop-down/flyouts so that they don't interfere with organic mouse motion and course correction.
I am not satisfied that the term "grace period" applies since that term is associated with lateness and/or some undeserved discretion being granted.
I think it is important to be able to have a term to describe this concept: it is very ephemeral, but a powerful lever in evoking positive emotional responses in user experience.