The rumors I've heard make it sound like it's not even always about making people want to quit, it's about increasing the cost of staying versus some other tempting alternative.
What I heard has to do with how they had Mauro do a show for all the fish, not just once but twice and one of those times with TTS and with Jet specifically directing the fish to pay attention to it, explaining how many followers everyone had gained on Instagram and how big CNN interviews awaited everyone. The insta followers for Vance and Sylvia shot up by 10,000x in the span of a day, which seems likely to have been done so they could show the two of them those numbers downstairs.
Sylvia was blatantly throwing during the PSAT, pausing and asking what section they were on and staring at Sam and just goofing around.
My conclusion is that Sylvia was ready to go home, finding that the (fake) increase in her followers was reward enough.
Ergo: It may not always be the stress that forces a fish to leave, they may be tempted from the house, lied to, and baited into going. Thinking about this actually disturbed me because they did take Vance out of the house to do the WP2 sketch, but I guess they're just considering that to be excused because they can't change when that sketch would be happening. But they could easily have said, alright Vance, do you want to be in WP2? Step outside, okay? OH YOU FELL FOR IT, STUPID, GO HOME.