I have big issues with the reasoning used to claim that Ben's universe is more that 1 universe.
I see no reason to believe the Space Beyond contains any & all kinds of realities rather than universes similar to Ben's own universe; If it has all "Branch Universe Clusters" then this only tells us that that's where you can see
branches of the universe, weird dimensions w/o regular space, stars, planet Earth and the human race aren't branches of the universe, that would only refer to alt./parallel universes that all come from a same og universe ("og" as in since ancient times og, not the og series).
When the universe clusters get detroyed and only No Watch Ben's universe cluster remains it doesn't mean that each universe has other dimensions, but that they were not targeted.
The idea of ignoring how Rex's universe is a universe because that's from his show and not said is the crossover when both are canon to each other doesn't make any level of sense at all, it's a universe, it doesn't have a Ben with a watch, wanna know why? Because both separated shows do their own things and that can create inconsistencies, the short version is just "it's an inconsistency". Things like beings being banished "from the universe itself" into Null Void
explicitly mean that pocket dimension isn't in the universe, when we used an
inconsistent technicality to claim otherwise, ignoring the other reason that makes that wrong. One thing is a verse being able to have 1 universe with many dimensions in it, another whole other thing is to make that up when it's not stated and is contradicted by those dimensions being outside the universe/time/space.
I'm sure some will think, if not necessarily say, that why
doesn't the Space Beyond have other realities other than "our universe"-like universes, that if it shows those shouldn't it show everything? No. That's a headcanon, the place that has universes but in present tense can have whatever rules the writers felt like, non-"our universe"-like universes too can have whatever rules in terms of positioning/structure and what makes their names all not just "universe" if some are sometimes called that. It's not mandatory that if you are in some place that's the space between universes it has to also be the space between dimensions when there's any implied difference in value between univeres and dimension.
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@Maverick_Zero_X Put very well I what I think of the multiverse being infinite, I agree with a "Possibly" for the same reasons.
Pocket dimensions can be infinite in size, their "thing" is that they're either literally in a smaller space on the outside than how they are in the inside or simply small portals/doors/whatever things are used to travel to them, while they're not even necessarily something that exists inside the universe. That said the evidence we have for Null Void being infinite is pretty barebones and insufficient.
I still agree with deeming that comic canon, since I'm ok with a simple yes or no to answer something based on canon is canon.