Or simply, just as turn based is wished to mean exclusively ugoigo, tactical RPG must mean exclusively XCOM like stuff.
Science fiction is anything published as science fiction. It looks like a weird definition, but that's how tags work. That's exactly why all the vain attempts to precisely define what RPG is are vowed to fail, it's mechanically easier to extend a tag than to restrict it. And no despotic fan community will stop other people to use the RPG tag.
And that's why Diablo like genre really exist, from the number of games arguing in their com their strong links with Diablo, or from people arguing it, communities of fans, reviewers, writers, you tubers, and so on.
The point is past XCOM release many games argued have XCOM qualities, and some about being an XCOM approach.
I don't remind that western Tactic RPG existed before XCOM. I doubt it's ever been evoked for Temple of elemental Evil, and Western RPG left promptly turn based. But for sure it doesn't make XCOM like the new Western Tactic RPG, it's more projects encouraged by XCOM sell success.
So most Western Tactic RPG are past XCOM release, but there's definitely something that occurred that was wider than XCOM, and that was about turn based. And clearly crowd funding is the origin, not XCOM.
So I buy that Western Tactic RPG doesn't make XCOM clone. Blackguards series and Banner Saga series don't qualify. But it's more perverse than this affirmation. Western Tactic RPG doesn't seem a tag that makes sell, many people believes XCOM tag has much more chance to achieve it. So more Western Tactic RPG will want evoke the XCOM tag than Tactic RPG tag, more reviewers or fans will use it. This would build an XCOM tag.
There was a dynamic to build an XCOM tag. But it looks like it won't happen, there's missing another game not XCOM and using the tag and selling a lot. And XCOM 2 sells failed build a second chance through a second wave so it will probably not happen even if there's definitely multiple games that contributed to setup an XCOM tag so the genre, even when going further than a very precise cloning.
So for sure any Western Tactic RPG doesn't qualify for building of an XCOM tag. But some of them very clearly contributed because of their com and/or comments about them, as for example Hard West, but not at all Divinity Original Sin.
And that's why Hard West is XCOM like and not Divinity Original Sin. Your opinion or my opinion doesn't matter, it's all the speech around Hard West that matter.