while currently doesn't have any running series? considering it is their main source of income?
and the magazine just okay with it being just one-off?
sounds like a vanity project then
Magazine editor are usually okay with it since in the same magazine, there are series that are often go on hiatus or irregular publication (conan, Frieren just to name a few) so they need someone to fill the pages.
Kotoyama also haven't released any oneshot anthology, so he can probably release a book if he do another oneshot or two after this.
Even without running series, he still get loyalty since his previous series still sold well, not to mention loyalty from international publication