As long as the wireless controllers don't cause stupid issues like the PS4 has been doing in recent tournaments then there's no issue. The main problem with wireless controllers recently hasn't been latency since the technology has come a long way, but the fact that syncing and interference issues can be a major concern.
It would be interesting to see this sort of experiment performed in the environment of a major, where lots of people have controllers synced and phones everywhere.
Still though, a wired connection should theoretically always outspeed wireless, so I wouldn't be surprised if the GC adapter has deliberately programmed input delay to keep it consistent with the other controllers. In fact it's interesting that all the controllers are so consistent in their latency, that flat out shouldn't be the case without a deliberate effort to make it so.
I honestly just wish this push towards wireless only would stop, there's a reason why all top quality electrical equipment isn't wireless, and while we're not asking for gold plated connections, please just give us the option. (Although I guess with GC at least they have, but I wish other Wii U controllers could be wired too)