I’ve had multiple jam up in my pocket just from general damp. At least one so bad that it needed pliers to force it open.It's not a myth though..you have two people in your own thread saying it's happened to them, myself included. Mine wasn't even submerged.
If it was your own creation I could understand your defensiveness, but unless you're secretly Pattree Opinel, I think you can accept that the wood they use sometimes swells!
I love Opinels, I'm not saying they're not great things FYI.
I’ve also had one have the handle shrink in the warm and caused me to cut myself when I put my hand in my pocket from the blade dropping loose.
That was when I ‘invented’ the locking function long before opinel themselves started using it for the closed blade and all excited posting about it discovered others had already done it too.