Absolutely, yes, refusal of engagement. But the number of levels upon which he can engage or refuse to engage are more complicated than just "facile" or "never let go." He and Prince Ji know they're using each other, but they still like each other. I guess I'm saying that taking what people are willing to give also means meeting them halfway: noticing Xia Dong's injuries and risking his life to protect her (even with the understanding that she's probably using him), knowing that Mei Changsu doesn't consider him an equal but still smoothing MCS's way with his father (where he rushes to explain that MCS was chronically ill when Yan Que needles him) and expressing regular concern over his health. He may even be so close to Jingrui because Jingrui does give everything in his friendships, and so Yujin rises to meet that.

There's the bit where his father is talking about working with MCS because he's supporting Jingyan, and Yujin doesn't say, okay, dad, if you think that's the right thing. He says, if you and Sir Su have such faith in him, then I will, too. I don't think he gives up on MCS even after what he did to Jingrui because on some level Yujin expected him to do it, and so he can keep the qualified trust that he and MCS have built up with each other, because it was never the wholehearted trust of Jingrui that MCS ruptured.