Why would I make that up?
I've got a swell idea! I'm going to go on talkbass, and just make stuff up out of thin air, yeah!
It happened on my fretless Dean bass. I put flat wounds on it, to keep the fretboard from wearing out (plus I kind of like the tone), and it didn't get played much, and sat in our engineer's studio for like a year. When I picked it up to play it, the bridge was lifting off of the body, and bending. I can only assume it was from the higher tension of the flat wounds. You know how if you let an instrument sit for a while, and when you pick it up, it's sharp? I think it was like that, except the cheap bridge failed.