It's just that she's been so visibly jealous of Shen Wei, but now that I think about it, I'm not actually sure how much of that happened where Zhao Yunlan could see ...

He might have interpreted it as platonic/professional jealousy or protectiveness or something? Idk, it's hard to strip out what we know (from the drama as well as the novel) and see it objectively from his pov...