DateTimeImmutable::modify() return type: doc or language bug?

Hi, DateTimeImmutable::modify() is documented as returning DateTimeImmutable, but it seems to actually be more specifically returning static: https://3v4l.org/j9ZSo Now I'm wondering whether this is a documentation issue (where it should return static|false and has not been updated to account for that return type's availability yet) or whether this is a language issue and the method is supposed to be returning DateTimeImmutable instead, though that's probably a considerable BC break. If you agree that it's a doc bug, I'll submit a PR. Regards, Philip