Jian Yi comeback?

Does Jian Yi come back after high school is over? I'm rereading and I'm confused about this point, he came back (chapter 45) Zhan Zhengxi casually states that he was his best friend (which they were more than that) after all the drama they went through together, which I assume was middle school, and Zhan Zhengxi just nonchalantly states we were in the same class and did homework together.. etc etc and when Jian Yi finally comes back.. their reunion isn't emotional at all!! considering all the things they went through in middle school... their interaction is more casual and restrained bearing in mind all the memories they created together, the confession, the fights.. so on, and Zhan Zhengxi leans more to showing more emotions comparing to the other couple, mo guanshan.. so while I was rereading, I was surprised how their reunion was very~ casual! it made me sad... please can someone clarify if I'm misunderstanding something.