Problem with "detecting" Opers with a WHO #channel is that there is no guarantee that someone will oper/deoper themselves. mIRC would have to "constantly" WHO #channel to keep up with that.

In addition, mIRC would have to USERHOST every JOIN to a channel to check whether or not someone is an oper. This would be extremely taxing to the network.

There is a reason why channel functions are kept separate from global functions on the server side.