My brother in law had a kidney stone, and one big enough to be removed bia surgery. He is a blacksmith, and continued working with the pain.
Just a little example of a case, to reflect, not only how fake his tale is. But also, how big of a whiny baby he is and a slacker bastard, if true.
So, I'm not trying to defend the dev or anything, but I literally just passed a 6mm stone last week which was lodged in my left ureter for almost 2 months, ultimately requiring ultrasonic pulverization to pass. Some days you may be fine, but some days you just want to curl up into a ball and die, and those bad days really leave you with no energy or motivation for the good days.
Funny enough, the fact your brother in law's stone required surgery means it probably didn't hurt all that much (relatively speaking), as they're only removed surgically if they're too large to pass out of the kidney into the ureter, which is where the real pain starts.
But anyway I literally just stumbled into this thread to see if there was any update to the game I downloaded a few months ago and saw this - sounds like this dev was pretty flaky to begin with so he may well just be looking for an excuse, who knows. Just wanted to lend some context to anyone trying to play off kidney stones like it's nothing - the pain is literally worse than childbirth and likely the worst pain the typical human will ever experience.