It is a bit more complicated than that. Basically, people you play with won't care so long as you've painted it to a reasonable standard and there isn't some massive size difference that'd give some notable advantage or disadvantage compared to official minis. The same is true of official ones where people are picky about unpainted plastic but its likely more a thing with printed ones. Independent game stores also won't really give a shit since you're likely buying paints and stuff from them anyway.
GW stores are the ones that will have a problem with it, along with tournaments they host. I have heard stories of people getting shit for using forgeworld stuff (which is GW's speciality site basically, they sell the really big models and some more niche like, regiment-specific stuff) in stores because it isn't something the stores themselves will specifically sell. This is because of corporate policy though, no one wants to lose their job.
Its as close as possible to now before the 50s