BF pretends to be happily married family man at work, then yells at his GF when she accidentally lets it slip to co-worker that they're not married

Note: I have edited the post to remove any references to the original subreddit to which it was posted. Below is a direct copy and paste of the post, with the brackets solely removing the identifying features of the sub. Bolded text are my own words.

"[Am I in the wrong for] telling my boyfriend's co-worker that we're not married?

I've been with Boyfriend for about 5 years. We live together. He does not want to get married, which I'm fine with now, but it was a point of contention early on in our relationship.

Boyfriend was talking to Co-worker on zoom when I brought him some coffee. Co-worker said something like "so this is the lovely wife I've heard so much about". I said something like "thanks but we're not married". He said "oh, Boyfriend always calls you his wife", and then introduced himself, I introduced myself, then ended the conversation and left as quickly I could while still being polite because both Boyfriend and Co-worker were giving me a weird vibe.

A little while later, Boyfriend came out of the office and asked "what was that?". I didn't know what he meant so I asked "what was what?". Boyfriend then said that there was absolutely no need for me to correct Co-worker and that it's better if people think I'm his wife. I said I'm not his wife, I'm his girlfriend, and he never told me that he told other people that I'm his wife.

This somehow becomes an argument, with my side being that Boyfriend never told me that his co-workers think we're married, and Boyfriend's side being that I should have figured that being called his wife indicated that Co-worker thought I was his wife and I shouldn't have corrected him, and when I said I thought he'd just made an assumption, Boyfriend said that wasn't the point, the point was that there was no need to correct him, that it was rude, and that it make Boyfriend look like a dickhead.

He then said that the solution to this is that when he next has a video call with Co-worker, he wants me to come in again, strike up a conversation, and say that I was messing with him, and that Boyfriend is actually Husband and us not being married is an inside joke I thought Co-worker was in on.

I then said that was the dumbest fucking plan he'd ever come up with, and "no fucking way am I doing that", and he said I was being an arsehole, that I got him into this, and now I have to bail him out."

OP concludes by asking if she is indeed in the wrong and whether she should "bail him out." Also, I will take advantage of this edit to point out u/Dharokalus's excellent note about how OP's bf might have started the fraud because married men make more in the workplace.