One problem with this poll is that it's not clear what an 'encounter' is, from the poll's perspective. The scenario you describe above is what I would think of as one encounter or one combat, with the opportunity to defeat the enemy in detail if you're stealthy and clever. Conversely, you can defeat them all at the same time with a suitable-placed Meteor Swarm, even the ones who are still sleeping/outside/putting their armor on/etc. As a DM, everyone I'm tracking both onscreen and offscreen as a potential combatant is part of the same "combat."
Well, in that sense then a whole dungeon one encounter! Any of the "locations" in PotA are one encounter if you consider that enemies can go get help the basis for the same encounter.
The thought is:
Trigger encounter 1. Enemy goes and gets help. Help returns triggering encounter 2.
The PCs options are:
a) Don't let enemy get away. Finish encounter 1 and start encounter 2 at their leisure.
b) Finish encounter 1 quickly before encounter 2 starts if possible.
c) "Let" encounter 1 and encounter 2 combine to deadly encounter 3
d) Run Away at any time
etc.