So if you're gonna wind up with 50 m/s left in your upper stage and you have hotstaging enabled, then when the upper stage is burned down below your lead time, it will begin to hotstage, even though the burn doesn't need the upper stage -- wasting an ignition.

Particularly with PVG where we have good data on if we need the upper stage or not, it needs to be able to avoid doing that unnecessary hotstaging -- probably with other ascent modes it is on the user to know if the upper stage is required or not and to manually set the autostaging cutoff.