There is no likelihood of success to determine -- if I meet the prerequisites for casting the spell, the spell happens. There's no saving throw for Wall of Stone -- it makes a wall of stone. This happens. Further, the GM can narrate whatever the GM wants, so long as it's a wall of stone appears where I say it does. With regards to authority, that's my authority, not the GM's, even if we pretend the GM has to speak it for it to be so.
And that would be the blatant deployment of Rule 0 Force that I mentioned in my first post. Either spells work, and the player is wielding narrative authority, or the GM is forced to be obvious about GM Force.
Well, no, because the player is not guaranteed a roll. I'm a very indulgent GM when it comes to these things -- I generally will call for a roll and abide by it -- but, even with that, there are some things that just succeed or just fail. "You learn the NPC is afraid of spiders." "Cool, I befriend the NPC by casting an illusion of a giant spider and saying 'want to meet my hungry friend?" That just fails, even in my games. But I could do that, terrify the NPC, and then cast Charm Person and, provided a failed save, they're still going to be friendly to me for the duration. And still scared of spiders, so any future asks might get disadvantaged if you keep the illusion around.
The point is, that Charm Person requires the GM to narrate the the NPC is now friendly. Just trying to make friends doesn't require the GM to do anything at all. Hence the nature of authority.
The difference is that spells require the GM to narrate specific outcomes. Non-spells do not.