If I were you, I'd have mailed grievance email id with screenshot of the offer and ask them to make millennia LTF instead of upgrading to a higher card (regalia, according to them). Regalia is useless for CB/rewards these days...
But needs differ and you might not have found any other way out for getting a priority pass (I think those aren't free anymore with regalia).
PS - I too got the regalia offer and converted to millennia LTF attaching the screenshot. Yes, some spend based conditions were there.