Lets split kanji of 异世界(Isekai), 异(I) = Another/Different, 世界(Sekai) = The World ; Different World
Isekai : usually referring to which revolving around a person or multiple being transported to or trapped in a parallel universe/another world or vice versa via either reincarnation, summoning, or a god transmigrating them.
So the isekai tags are correct