User status `spam` is supposed to be multisite-only, but shows in single site?

Filing issue, because we actually need this functionality on single site, don't currently have a `spam` status implementation, but unsure whether it's reliable on single site.

https://codex.wordpress.org/Function_Reference/update_user_status#Mark_a_User_as_Spam says "multisite only".

Is exposing this status on single sites a bug, or a feature? What to do next sort of seems to depend on it.