would explain his reaction in the new timeline when he was watching hayeon and yihan from the closet
ALSO,,, in the character sheet it says one of his biggest regrets is not forming a relationship with hayeon 10 years ago. that's why he's trying a lot more in the new timeline!!!!!
He also said "the last time" when visiting Hayeon's house, while in this timeline he had never been. He then said "what i want the current you can't give". So yes, he is definitely from the other timeline too.
That's what I'm saying
jinwoon definitely came from the past too or at least has some memories of it.. he knows too much