Why does something happening identically in one multiverse mean it's the same multiverse? Even in the same multiverse, 2 universes could hypothetically be the same - this doesn't mean they're the same universe, it just means they're identical. It'd be like saying the DC comics multiverse is the same as the Marvel comics multiverse - they both have different, fleshed out multiverses, yet they cross over with each other, since there are clone universes in the marvel multiverse. Since the MCU is an adaptation of a multiverse, it is set in its own, unique multiverse.
That's just my take on it though, I don't believe it's been confirmed nor denied (other than a book from years ago stating Earth-199999 is the same as the main universe of the MCU - though since the MCU is a multiverse, not just one universe, this would be irrelevant).