Also...and bearing in mind that I'd have to look up the formula's...when you start doing the math on "10% tolerance" on a capacitor, you end up with what my first semester electronics teacher said was an absolutely negligible amount for most practical applications; and yes, filtering frequencies was the name of the game. Resisters are a totally different ball game, because of Ohm's Law and the direct effect that resistance has on current, so those often require a tighter tolerance. Which makes your point about the pots valid. BUT, even then, it's not at all RADICALLY different going from 500K to either 450K or 550K. There's clearly a bigger difference between 450K and 550K, but it's still highly HIGHLY likely that the difference can be filed away as "Meh, whatever."
This is an opinion. Everyone's got one, and they all stink. Way ahead of you on that one. The reason for this opinion is that if there was a big enough difference, then guitar manufacturers would have tightened the belt another notch a LONG time ago due to complaints from the anal retentive customers we often tend to be. Plus, I can almost remember some this one from vocational school (and now we're up to third semester...rolled my car, got a DUI, coasted through the rest of the semester, failed, and dropped out), look at the frequencies that we're dealing with, and the effect of changing from 450K to 550K ohms. Then compare that to the human audible range AND sensitivity to changes. My first thought is that there's only a small percentage of people on earth who can pass a blind test on this one.
Think of bending notes. If you're just sitting there and it's like, "Okay, this is a C, and now it's a C#." Use your tuner, and a decent guitar player will hit it dead. Now start jamming. How close are you now...??? And can anyone in the audience really notice if you're a few cents flat or sharp, even if you hold that note for long enough for it to truly register in their brains...???
THAT is the level of difference between 450K and 550K ohms in a volume pot when talking about which frequencies are actually being combed out or left in. And THAT'S why they still put "crappy tolerance" pots in a guitar.
Again, I haven't done the math, but I did go to school (and have nothing to show for it), and this fits right in with what we were being taught about how much we should care about the tolerances of standard "solder-in" components when the frequencies aren't at, like, AT LEAST megahertz, and more like gigahertz and beyond.