Yeah, losing the stickiness is a better indicator to me.
Not all vaporizers/temp settings/etc. produce that flavor and some will do it even before the load is completely done. If I try to dump it and some holds onto the bowl though, I can still get some extra vapor out of that before it stops holding on falls out too.
Still, in many cases the burnt popcorn smell/flavor are a good indication that it’s at least done enough for me to dump it, so I don’t think we should ignore it as one way to judge what’s left in a bowl.