It's entirely possible the joystick mfg cherry-picked the pots, or had the pot mfg do it for them.

I had to do this once when working at a thin-film hybrid shop making microwave amplifiers. The amps bought to spec were so expensive that we'd just buy hundreds of lower spec amps and test each one. I was just a pup out of school back then. Now I can't imagine that the company actually saved any money doing this.