Why aren't boosted players being cracked down on harder?

I just encountered a Diamond V player who I reported for being boosted last season again today, meaning no action was taken against it. It's once again been boosted back to Diamond V.

When we got into the lobby, our top player asked mid (the boosted player) if they could switch. The boosted player says 'no, I don't play top.' I look at it's statistics for this season, and it's most played champions are Irelia and Pantheon with combined 85% win rate, yet it claims it doesn't play top. Looking at it's history, 90% of it's wins are playing one of those two champions, duo queued with someone else. All of it's other games are as Annie and Ezreal, queued alone, and they're all losses.

If I look at it's pre-S6 statistics, it mains Annie and Ezreal, and was Silver until last season.

In the lobby, I said 'If you don't play top, then you're boosted, because your most played champions are top,' and it dodged.

How the fuck can this player not being banned even be justified? What's the point of reporting this if nothing is done about it?