In college they're in their own world most of the time. They're not expose to many interaction. He actually shows his possesiveness in earlier chapter when they're not together yet. He almost crushed a dude's hand because he's touching Jiwu.
The uke too... where's his obsessiveness
Idk if we're reading the same manhwa but the whole story started because Jiwu is stalking Jonghyeon (top), and he even confessed to it. His character has always been consistent and he also never hides the fact that he likes Jonghyeon right from the start.
Why does the sunbae's personality seem so different now from when they're in college