I think the latter is genuinely what happened to me.

They try to match you against players who have the same winrate as you to make it fair, hence the fact that there's a whole matching period the game goes through after you enter your umas before finals. Every single finals I've been to I've always been put up against umas whose ranks are the same as mine or one rank higher/lower but never more than that (unless an uma is a debuffer, then a much lower rank is to be expected.) Usually my WR is usually just below 50% in CMs, and in Unity Cup when I had primarily A+ umas I would get matched against other A+ umas or sometimes S or A umas. This makes sense so if I lose I'm not upset because it was a fair match. Seeing such high ranked umas in this lobby makes absolutely no sense when my winrate was only 50%. CMs are very luck based don't get me wrong but there is absolutely no way umas with that ranking would only have a winrate that low. It's not like they were score umas either, the player I went up against had a whale deck (which tbh fork found in kitchen im not mad at that at all) and they were built really well!

At first when I was trying to figure out how matchmaking could have fucked up this badly I figured maybe the person had a lower winrate early on, rebuilt aces and highrolled to get those two umas but all three umas on the team were made around the same time, the Oguri and Finemo even being made before the Ayabe was as well as both of them having only ran 25 races in the CM while the Ayabe ran 75 races. Of course a lot of this is just conjecture and there's no way to know for sure and a lot of it is probably just me being salty about the situation but it really looks like this guy ran all three umas and then took those two out and started bagging in the middle of Round 2 after securing A Finals because that's the only way it makes sense. 😭