Yeah it feels like an easy method to hand wave inconsistencies as they happen in the show. It’ll let Pennywise attack up the family trees during the next few seasons so I forgive it there, even if it makes It look like an incompetent villain in the long run.
It was an alien in the book, the species is hinted though never fully explained in the Dark Tower. It does exist out of time there, but more as a cosmic being than how it was shown in the show since the details are left out.
At least as far as I remember, it’s been a few years since my last trip around the wheel.