My husband shared an office with a woman for about two years. She recently moved to a different division and they rarely see each other. She and I joked about her being his work wife, but only in a "you're the only one who knows what I put up with" kind of way.
As a joke, I found it amusing. I wouldn't if it were some kind of serious term. I also wouldn't have found it funny if I thought they were at all interested in each other. That simply wasn't the case. She is a lovely young woman who had come to dinner at our house and invited us to hers. We talked about our churches, her dating life, our kids, etc. They were friends and by extension I was as well. I suppose some of what made it work was that they were different generations, different religions, different ethnicities, very different ways of looking at life, etc. Not exactly a match couple wise, so it was amusing. When my husband would crack a joke we would roll our eyes and say to each other "finally, someone who understands what I have to put up with!"
I can certainly see how it wouldn't have been amusing under different circumstances.