You shouldn't need to jump down. As you initially suspected, interacting with the hole is enough for your character to know about it. But just visiting the zone and seeing the hole isn't enough, you have to click it to examine it closer.
Something about this dialogue isn't working correctly. When I talk to rejects, they start dialogue from the very beginning each time I talk to them.
I was able to talk to them about escaping to the vent first time but since I did not interact with the hole, I was not able to make them escape the first time I talked to them.
Now I don't even have option to talk to them about the vent.
tl;dr:
you have to interact with both dialogue in hand:
1. Escape through vent.
2. Then use the hole in the ground to escape.
Otherwise it just breaks. No way to make them escape.