I’ve gotten several comments deriding me referring to an Elizabeth Line station as “a tube station” but so far—despite my requests—nobody’s explained WHY.

Is it NOT considered part of the Underground?
It has the same logo but in purple, which I assumed was just for Queen reasons.

It interfaces WITH Underground stations, does it not??

Is this a colloquialism I just won’t understand?

@Graham_LRR I'll preface this with, no one should care enough to correct someone about it...
But purely to answer the question It's an overground line with some underground sections, so technically hybrid (and run by MTR rather than FTL if anyone cares). It's officially not part of the underground
@ramchale @Graham_LRR ah, so it’s not the Underground, it’s just Sparkling Metro