On the idea about the stones working or not working, you kinda have to throw out the comic canon where they shouldn't since MCU, at times, does its own shit. In this case, the stones don't work in the TVA as a specific safeguard in the TVA... but it doesn't quite include the multiverse in the MCU. The MCU idea of "branching timelines" is the basis of the movie universe multiverse, and since this shit is basically splintered time paths from the same vine instead of distinct numbered universes running in some sort of interdimentional parallel, they are *essentially* the same universe. There is a lot of conflating of timeline divergence and pure multiverse theory here just to make stuff plot convenient... like the crusher not working, but two different time stones exist in a third universe and both work.
I'm thinking, ultimately, we're not supposed to think so much about it. The more you think about it, the more it falls apart, but if you look at it only at face value, it works well enough to seem legit enough to buy. Sort of like how Magic and Science started off as essentially the same thing based on level of comprehension, but later being defined as two entirely different things.
Arguments about stones aside; I liked it... but*
I was a bit disappointed. I mean, nice to wrap things up like that, but even the title of the episode implied something it never touched on. "What If... The Watcher Broke His Oath?" Apparently, the answer is nothing. There was no consequence of his interference, right, wrong, or indifferent. The oath is just there as a matter of principle, then?
It's one thing where Demon Strange became so powerful that he could actually percieve and communicate with him, but it's quite another when he could just plop apocalypse Natasha in another universe.
The stone thing was easy to ride past for me, lest you fall in the quagmire I went into before about what the stones should/shouldn't do vs what is plot convienent and canonical for the MCU, but this was alluded to have some sinister cosmic consequences for actually sticking his nose into events and affecting outcomes. And even though it wasn't exactly his fault Ultron expanded his mind enough to put all of existance at risk, what was the Watcher's prohibition besides his own word?