I don't see what the big deal is.
The hiring was for a designer. The designer is arguably what makes the game. Or at the very least, if a designer fails and everything else is good, the game is still probably going to be a flop.
It doesn't matter that designers on sub 85 metacritic games might be good, what matters is that designers on 85+ metacritic games are more likely to be good, since design is such a heavy influence on how well a game is received.
Furthermore, while an 85+ metacritic is not necessarily an indication of how good a game is, it is certainly an indication of how well a game sells (as in, not many games with 85+ metacritics bombed, although it's happened), and it is pretty normal for a company to want their game to sell well.
There are also fewer designers on a project than other roles, so each designer has a much larger personal impact on the success of the game than, say, each programmer.