You can pick at powershell for many things, but it's help implementation soundly thrashes "man". It's not even a contest.
Sure, you may have a point on that particular issue. You are after all talking about a system that was made up from whole cloth by one entity recently, not an older system that grew organically over time at many places, with input from many people.
And the perceived lack of consistency of manual pages was indeed identified by the GNU crowd, and hence their trying to introduce the "info" subsystem (that addresses most/many of your issues).
And "info" didn't really take off. Why? Because man pages are just "good enough". They're certainly not so bad that it would motivate someone to change platforms to windows (not even "info" it turns out). Having tried to build serious systems on both windows and Unix, the amount of documentation doesn't really help, when so much of what Microsoft tells you is just flat out wrong as in "will not work as advertised," even in the technical documentation.
So is e.g. bash flawed? Sure, the semantics are alright, but the syntax is pretty horrible (hence Plan 9 and "rc" that I ran for many years, which is much improved and a joy in that respect). But, at least it works as advertised. (Note that "csh" that doesn't work as advertised, was pretty much dropped by the wayside a long time ago).
And that's why we do not care one iota that MS moves powershell to Unix. And why we likewise don't care much about arguments about its superiority. We've been burned hard enough in the past to have learnt our lesson. And "bling" like slightly better on-line manuals (esp. in the age of Google) doesn't sway us one bit. Not even a little one. So feel free to keep powershells superior documentation. It comes with much too much baggage to be worth it.