Is that a spoiler or your theory?
Well... What ever happens there needs to be chasing and grovelling arc for ML... And it better be long and suffering one.
I'm imagining Pilsang going to live with the woodworking grandpa and when Jooen comes in he just act like ML is air... Thou knowing Pilsang's character, he probably is too much of a softie to do the ignoring, despite how hurt he is, so he probably runs... Just dunno how and where he could run without ML instantly finding him.
So most likely your theory is correct... Pilsang just leaves and Jooeon tries to act like it doesn't matter so it takes awhile before he even bothers to chase.
Thou I would hope that Pilsang isn't the one to confess first. It would be so much more satisfying that Pilsang leaves before confessing and ML needs to confess first.
Or if Pilsang is going to confess first... When ML confess later, Pilsang is so hurt he won't believe or trust him at all. So ML's confession is basically worthless.

I know where this is heading and I am not happy about it.
Jooeon about to fuck up a good thing thinking it was all just a calculated game. Watch Pilsang confess in like 2-3 chapters and we will either get bliss for a while or immediate Jooeon acting flippant because hes "won".... then a chase arc because Jooeon is going to try and move on with the marriage because hes "unaffected".
Pilsang will run away and Jooeon will be back in house pretending everything is okay.But when he finally opens Pilsang birthday gift to him he's going to remember how much enjoyed Pilsang and being with him.
Pilsang you bet not give in and make that man GROVEL