Even this isn't really needed. For example, if I have two 2D planes that are separated across 3D space and are perfectly parallel to each other I could topple one of them just 1 degree in the direction of the other, they would maybe cross in a specific line, but they would still be embedded in the 3D space and mostly separated to each other. So having points of areas that are common to the universes isn't something that really stops them from existing across a higher dimensional space and being four-dimensional space-times themselves.
In the end, it really will depend on the series. We can discuss rules and standards here, but most of the time what really matters should be defined by the work itself. When the work has basically no description for its cosmology we are basically just guessing how that cosmology works and what could be a reasonable tier, but that is where you'll have vagueness, and not everyone will agree on what should be the standard just due to how all over the place various cosmologies over there that you can really question "what is the most valid possibility".