It looks like Jian Yi is very uncomfortable by He Tian’s flirting. Every time He Tian come up to him to flirt around -alone or in front of people- Jian Yi keeps rejecting him. It’s only him though. Jian Yi has no problem with having other guys hug him. Remember the chapter in which Zhan Zheng Xi was looking all pensive, staring at Jian Yi being hugged and close with those two random guys? Jian Yi looked happy and not uncomfortable by them. When He Tian tries to do something similar, Jian Yi rejects it.
So it looks like Jian Yi just has a personal space/flirting issue with He Tian not in general.