
Ehhhhh I don't think an "I love you" would make all that much of a difference...
From my perspective the issue isn't Shin doubting Wolfgang's feelings or anything of that nature. I believe he knows how much Wolfgang cares for him and how much he cares for Wolfgang and that's what scares him. He's terrified that one day those feelings will become Wolfgang's weakness and put Wolfgang in harms way or jeopardize the country. An "I love you" isn't going to make that all go away...
I think part of the reason Shin says he's just a prize or continually reinforces the idea that he's just a subject and Wolfgang is his king is because he's terrified of it being more than that. He has a hard time facing Wolfgang's feelings for him and even more, he rejects his own feelings of love for Wolfgang. Shin is the type to always put his duties above himself, he would choose what's best for his king and country above himself. He probably feels that loving Wolfgang, not as his king but as a man, is selfish of him and that's part of why he has such a hard time admitting his feelings even to himself.
I feel like the main obstacle won't be completely solved by them confirming their feelings to each other but rather by Shin overcoming this fear and allowing himself to love and be loved.

Well...I personally wish this chapter didn't happen because I don't like things like this hhhh but I don't blame the seme at all. They weren't actually together at the time just fuck buddies, and what the uke said was very hurtful so I can understand why the seme would do what he did. I just wish he didn't go through with it to the end because I don't like things like this and it just makes me feel ugh hhhhsfdkjs;dl but I do understand why he did it. Since they were already together and happy and in love at this point in the story, throwing this bit in at this point dampened my mood quite a bit. But it was still cute and sweet and I was glad it got resolved quickly and the uke was honest about his feelings in the end.
I know it was normal for royals back in the day but man...I would feel SO awkward taking a bath in front of all those people lmaoo and all the paper/books near water makes me so paranoid omg. I get anxious during these scenes but luckily Wolfgang's hot bod provides enough distraction ლ(´ڡ`ლ)