Pretty sure matchmaking is based on the top 5 heroes in your roster and NOT your defense. This was changed way back because it was too easily exploited. So if you put that out defense, not only will it be E throughout the week, but you’ll still end up fighting 4600+ teams.
I know who you’re talking about, I’m pretty sure he did not get A defense throughout the week. I have no emblems on any 3*, but troops at lv 5. A defense throughout, and 4 or 5 losses but still managed top 1%. Actually reading that thread again, seems like he didn’t do the last 5 attacks because of something he had to deal with in real life, so that would explain why.
Edit: Ok found the post. Apparently went 19-4, so didn’t even do the last 2 attacks, potentially missing out on 1000 points. But because defense was A grade throughout the week, still managed top 1%.