That’s according to Mrwhosetheboss, whose Youtube channel I happen to like. He’s got a ridiculous 18 M subscribers, not that that means the content is worthwhile, but in this case it is.
Basically, the new M4 iPad Pros are fantastic “pieces of kit” as he might say (from his accent, he’s British I think), but the software is still borked, and crippled, particularly with respect to blue tooth mice and keyboard stability and multitasking. See this 12 minute video - https://www.youtube.com/watch?v=xNv2EOc6ma0