A 6 GHz radio is pretty much equivalent to a 5-point-something GHz one.
As a counterexample, 2.4 GHz is completely unusable in our penthouse office. I'd rather deal with limited cell size than continuous interference issues.
Yes, in an apartment, more available frequencies and less ability to penetrate walls is a good thing. Otherwise there’s immense amounts of interference. And it ends up being made worse when people try to improve their own experience by turning their transmit power all the way up. It necessitates that everyone turn theirs up, which then just makes the interference return and spread further.