I am curious, why do you think that? Now excuse me for intruding, but the way I read it, his romantic arc is about how our presence positively influenced him to find a new meaning in life. Yet the champion, as things stands, is a more reactive then a proactive participant in his journey, which would just make his proposal add to that feeling. Now of course if his expansion adds content where our actions take a central stage, him proposing again is fine.
Nevertheless, while I understand the appeal of having a twink try to wow you, I think champion having some sort of textual agency in who they want and do not want to marry goes a long way in making them feel like caring lover.
Tldr: He already proposed once. It is our turn.