My own experience as both player and GM, combined with conversations I’ve had with other GMs and players, suggests to me that this is very much not the case.But, it's not hard. That's the gatekeeping. It's not harder than playing, really, as you need to know the same general things to do both: how the mechanics work and the idea of a shared fictional space.
When I’m a player, I don’t need to know as much of the mechanics as when I GM. Nor do I need to know/think as much about the ‘shared fictional space.’