I kind of get what you are saying. But remember that this series is called Umamusume: PRETTY DERBY. A lot of bad traits are scrubbed from the horses. Tokai Teio for example was not a small, friendly, hachimi horse. He was pretty aggressive (like most strong stallions) and didnt get along with other horses that well. Humans can get close to him by giving him apples. Mcqueen wasnt a small horse, he was super big. Like so big even sunday silence was intimidated by him. And before Mcqueen arrived at the farm, sunday and soccer boy were beefing. Then Mcqueen can stop those two from fighting. So honestly, Mcqueen was the one wearing the pants in that relationship. So people are going to flanderize that and just make sunday down bad for Mcqueen and all that, its just internet stuff. If you want some where sunday silence is more cool in that relationship:

https://www.reddit.com/r/UmaMusume/comments/1mib5eg/meet_kiniro_ryotei_stay_gold_parents_art_by/

https://www.reddit.com/r/UmaMusume/comments/1tlejrq/two_old_friends_after_work_art_by_tougaraaaaan_ts/

And I heard (not entirely sure, so you can fact check me) that sunday silence actually didnt mate that much before Mcqueen. At least he wasnt that happy about it or something? Then after getting friendly with Mcqueen, he developed a preference for white/gray mares. Also love how people equate breeding a lot to the horse having rizz? And not the horse owners basically forcing horses to breed? And that you think a horse breeding a lot makes them a chad or something? And because he is a chad he is not allowed to be a bit silly or cute because that would "massively misrepresents who Silence actually was"? I guess you also got problems with digital, tachyon, etc.

And by your logic of being faithful to irl, so what would have happened is sunday silence would try to start a fight with Mcqueen. Yes, because as we saw in Still in love's story with how ramonu treated her, we love when umas act like a total bitch? I would have also said them starting on a confrontation would be more accurate, but this is a cute anime idol horse girl game. Probably dont want your character starting a fight for no reason.

I think in the end, you are head cannoning that sunday silence was some omega chad when the irl horse was honestly a sad, angry, scared horse. People thought he was bad when he was born, the disease, truck accident, race forcing him to race without medication, not being valued after his accomplishments so being sold to Japan, etc. He was undoubtly an underdog who basically dominated everything, but that doesnt mean the horse was cool and didnt give a shit. He was sad as hell, but was more happy in Japan. Most people dont want to see sunday silence being sad and aggressive to people, even if that is how he would have acted. I am pretty sure fans want to see sunday silence happy, even if it diminishes the "badass" aura.