It's been awhile since I've read it, but I feel like the novel handled explaining this better? I could be wrong though lol
I know adapting things can be difficult, but it is unfortunate when it feels like it has to be rushed a bit so some bits end up going missing...
(Unless it's a series that's supposed to be a companion to the novel so it's skipped on purpose, but in those cases it's unfortunate still since some people just prefer reading the manga version and there's nothing wrong with that so it's just a confusing mess...)