Leaverbuster… why

So I was playing with my brother, I was midlane and he was the jungler. He had a bunch of computer problems and showed up to the game really late, like I was level 10-11 when he joined. Instead of raging, he pushed through being behind, caught up, and became a big help in team fights (not gonna lie Gragas is a beast). Anyways, we eventually lost because our ADC left after giving up 20 kills, but I ended up with 30 kills and my brother had a lot of assists (don't remember the exact number). First thing after the game, my brother gets a leaverbuster notification and now I have to wait 10 minutes whenever I want to play with him (this was his first time being this late to a game in months). Our ADC on the other hand, didn't even show up as red in the post-game cha. I wanna hope that she got punished worse than my brother… but really 10 minutes before every single game due to problems out of his control even though he caught up and did better than the majority of the team… that seems unfair.

I hope someone from Riot at leasts looks at this or maybe even responds to this and explains why focused players like my brother who work their asses off to catch up after computer problems get punished while ADC's who feed 20 kills then AFK get to waltz off