I'm assuming ch 440 - 442 is still the original timeline and when HT decide to leave. At the end of ch 440 HT said he's going somewhere for a while and asked MO if he's not gonna asked where he's is going. Mo replied tht he's not gonna ask because he knows HT will always come back. The ending of 442 is the ending of the original timeline with the funny looking tree after the fight with she li looking from the context. Like maybe the tree was an indication of their story in highschool ending(?)
I'm also assuming the next few chapters are filler chapters and like maybe an AU of what they would do if HT did not leave bcs it also has brother Qiu's story too. Like very unrelated chapters.
Then the original timeline continued in either ch452 or 454 because we knew HT came back and they've all grown up. In ch454, Mo literally said "now that you're back..." So tht means we're back in the original timeline. So yeah this is what my speculation is.
Damn the time skip is so vague I got confused,,cs it didn't show He tian left explicitly and there were so many extra chaps,,but I love angst so this is goooodd