I don't know if I would call them a kpop group given they have no original Korean songs from my understanding, promote primarily in Japan, and their songs have Japanese most of the time. Same way I wouldn't call NCT 127 jpop, when they even go so far as to release original Japanese songs, which NiziU don't release Korean original songs unless I'm missing something. At most to me NiziU are a kpop styled jpop group.
yeah, and that's how you view it, and so do i. they're a k-style jpop group imo. i'm just saying that since they're backed by a korean company and are modelled after kpop groups, many people (including japanese fans, people from the country they belong to and primarily promote in) consider them kpop. similarly how most people would consider nct 127 kpop not because they mostly promote in korea and mostly release music in korean, with most members being korean, but because they're an sm group, with sm being a korean company. not that i necessarily view it that way, but some do.
that since since they're a jyp group i still think they could be used if jyp decided to launch a jyp nation superm style group. not necessarily their first choice though.