Who knows maybe they're tiny compared to the mortal realm, maybe the dimensional walls transparent much like the uh, dimensional walls we see in that very scene? Maybe it's retconned. Maybe the anime just went and did its own thing.
Don't know, don't care, all I know is that
it's the only actual time we see the universe without fluff and abstraction.
Or maybe they're just a part of it? Like WotK? We get like 3-4 zooms out in Super showing that alone, in the anime it def ain't enclosed
Do you not understand what this CRT is even about?