I think sometimes it's just easier to say husband instead of explaining a "it's complicated" relationship status. I have a really close friend who has been with her partner maybe five or six years. They have a 2.5 year old. My friend wears an engagement ring, but they really don't have any immediate plans to get married. Or maybe they never will. It doesn't seem to bother them. But they live together and (unlike PF) are very much together. I've been with her several times when we are around other people and often she will just make a reference to "my husband." Because he's more than just a boyfriend, and they have a child together. I guess she could say fiance, but there is no upcoming wedding or marriage plans. I think it just avoids having to explain or invite more interest or questioning into her personal life.
Even when I mention something about them in passing to someone who doesn't know them, I always stumble over how to refer to him. Like, "Oh, Mary's.... boyfriend? fiance? husband? was at the game on Saturday." Sometimes I would just say, "Mary's baby daddy" kind of joking because she does, but then a friend said, "You always call him that! I thought they were together?" And even though I was just kidding, I realized that sounds like they aren't still a couple. These days I will just say something like, "Mary's man's name is Joe. Let's just call him Joe."
It all sounds silly, but we do a lot socially with them and their families, so they often come up in conversation and I legit never know a quick way to describe who he is! And I noticed that she often just says husband. It's not trying to mislead or deceive, just kind of mitigates having to explain a private dynamic to acquaintances, coworkers, people more on the peripheral of your life.