They're not, we use guidebooks
very frequently
Only for canon are the universes finite, but for Toei and the games the macrocosms are infinite in size. This is because in Toei the statements on the universe having an edge by Bulma do not appear, unlike DBS.
Here are some threads to give context:
Toeiverse Universe So this thread is gonna be exclusively about the toei cosmology, since I don’t want to get into the controversy of Super right now. It runs through more smoothly if I focus on this one instead. Why should the Universe be considered infinite? There are a multitude of...
vsbattles.com
I'll be simple and direct here: The Dragon Ball Universe is cited several times as having an Infinite Universe both in extension and in "base" size the only contradictions in this exist (as far as i can remember) ONLY in the anime, where Super Shenlong is invoked and we catch a glimpse of the...
vsbattles.com
Though I must say I disagree with canon macrocosms not being infinite in size.