OK Here's the problem: This scene worked in BJ alex because Alex CARED about Dong-gyun rea...

OK Here's the problem:
This scene worked in BJ alex because Alex CARED about Dong-gyun reactions when they were having sex, even if their relation was messed-up and Jiwon was disrespectful he CARED about how dong gyon was looking at him because he loved him (even if he didn't realised it yet). He was actually hurt in his heart and pride during this scene.

But Jaekhyun DON'T! He never cared if Dan liked him or not, he always took his pleasure without being worried if Dan was enjoing or not. Jaekyun always considered Doc Dan as a hole, nothing more...
So it doesn't have the same impact, Jaekhyun shouldn't care that much since it's how their relationship always worked.