As usual, evaluating tier 1 CRTs feels like trying to read a scientific manuscript in a language where you barely know how to say "Good Morning". But I think I understand the issue here.
The universe in the Ben 10 cosmology is 2-A, as established from previous discussions. I've never been involved with these discussions, but I'm willing to assume this premise is correct and doesn't need to be debated here.
The Space Beyond is a structure that contains all of the universes (which are all 2-A?), of which there are infinite universes. Professor Paradox can access the Space Beyond, but states that Maltruant will be "beyond his reach" if he escapes the Timestream; ergo, the Space Beyond is within the Timestream. I don't know enough about the series to verify all this, or the stipulations that come with it (i.e.: Can Professor Paradox can access all of the Space Beyond? Are all universes 2-A? Are there provably infinite clusters of universes?), but assuming the information given is enough, this premise is reasonable.
In comparison to the whole Time Stream that Ben and Maltruant Fly through, the Space Beyond is infinitesimal. Can I get more context on this? Watching the clips provided, I don't see where this is confirmed. I don't see the Space Beyond that they travel through even referenced in the clip where they travel through the Time Stream; I suspect there's just some context not given from this clips that explains this away, but I need to understand this in more depth before I can agree with it.
Therefore, the Space Beyond is a Low 1-C structure because it contains infinite 2-A structures. This is where my brain turns itself inside out, as usual for tier 1 threads, but I think this does follow our standards. The Space Beyond contains infinite 2-A structures, and therefore those 2-A structures are infinitesimal portions of itself; this seems to fulfil the requirement for "encompassing them in an infinitesimal portion of itself" that's required for transcendence, and therefore Low 1-C in this circumstance. I would like to ask that someone highly knowledgeable in tier 1 standards verify this fact, however.
To summarise, then; I have lingering doubts about where the Time Stream falls into all of this, as I don't think enough context has been given to understand what its role is here as an outside observer. However, the information given about the Space Beyond (assuming all premises are correct and not contradicted within the show) does appear to fit our standards for Low 1-C. As such, I can consider myself a supporter of this change, though I would like all lingering questions to be answered before this thread is concluded. Most notably, whether all universes in all clusters can be considered 2-A structures, whether there is provably infinite universes, and the size of the Space Beyond relative to the Time Stream.