HN thread limit might cut this off but what if someone in that team starts experiencing problems and self-doubt? If everything in the team has always worked smoothly before they might not be able to handle it.

Additionally, elitist teams might scare off some people that could otherwise be great engineers if they just got a little entry help. Sure they can "get that elsewhere" but if every team behaved like that there's not only nowhere to enter, but there's also sort of an omnipresent assumption that you have to be good from the start in order to be able to achieve something in engineering.

I'm not saying your described team doesn't work but it's not exactly the kind of culture HR should be striving for in my opinion. (Albeit it's still far better than than a team that doesn't work at all or works against each other.)