Since this is a question here, there is of course plural in Japanese, it's just that just like with a lot of stuff in Japanese, it can be removed when context is clear and it's mostly not used as the border between plural and singular isn't often described in a lot of Japanese texts. For example,
in this text the word is "stars" and we can be sure about that because the original text is "星々". The first is the kanji for stars, and the second is a particle to denote plural (It's actually a particle to repeat the previous term because by saying the same term twice, it gives directly the notion of plural).
So, it's not that there's no plural in Japanese. There are many ways to denote directly that there are more than a thing in the dialogue, it's just that very often it's not something that needs to be done. Of course, even if there wasn't a particle like that (The example I gave before wouldn't work well if it was a very big word for example when reading, like the subspace example).
In this case, since the text was talking about something in a generic way and it gave examples of two spaces existing, of course the way I understood it was a generic concept to describe such places, not a singular place that emcompasses those other spaces. If someone wants to make that the interpretation, they could make it so it's talking about a singular space. I'm not a DB expert, so I don't have an opinon in regards to that.