I have heard it prior to it becoming the gay spouse word. It was used for couples who had been together for a long time, typically live together, but weren't married. I used to work for a man who lived this way. They sometimes referred to it as a partnership. They were successful, hard-working decent people, and raised an exceptionally smart child. The partnership was because she had been in a previous marriage and the ex-hubby was a real piece of work - and that's me being polite about a guy who deserved whatever form of justice he could get. Because of her experience with ex-hubby terrible bastard, she wouldn't marry again, but had everything else with her new guy. It was certainly understandable.

But that's very different from the GenZ's saying that today because they've been so inculcated in the Alphabet mafia's rhetoric, they can't distinguish between hetero terms and terms for the other.