I don’t think that it is what they meant. It’s more that only one case of experience doesn’t make a point.
For example: A computer power supply has an avarage life expectancy of 8 years if in heavy use. I have a gaming computer and - since I work from home as a freelancer - I use it daily almost aound the clock (I turn it off when I go to sleep and on when I wake up).
I’ve upgraded some parts over the years, but I’ve never changed the power supply. It runs fine since 15 years with no issues concerning the power supply.
I don’t have a surge protection at the socket. I plug it out after I shut the computer down. Those things do stress the power supply unnecessarily and I still don’t have any problems.
However, in the same PC, I’ve had the hard drive that came with it make a head crash half a year into ownership.
My grandmother across the street has these old light bulbs in her living room lamp. Since she moved in, about 18 years ago, she did not have to replace them. Meanwhile, my lamp ate about 1.5 energy saving lamp bulbs a year.
Those are all real life examples that go against common knowledge. I hope you see what I’m trying to say here: Just one experience does not invalidate other data.
As for the gun fouling, I would assume that that data was taken from average data available on the internet or in books. And yes, it was probably avaraged (or extrapolated) across all guns, which is not good, but there has to be a point where time wasted on researching and coding it for every gun, as you probably know from your own projects, gets too large to validate the small gain of realism from doing so.
So, to change that, we would need either a source that, like you said, bought 50 guns of the same type and fired every one without cleaning for enough time to gather reliable data, or find 50 people with the same gun, same gun usage and who also never cleaned it. I doubt that you’ll find these 50 people here in the forum.
The third way would be to check in with the manufacturer, as they usually run these tests and offer an average.
Also, while you state that you’re not asking for any change, it looks like you do imply it by asking “This game wants to stretch toward realism?”… which sounds like “This game is not realistic, because … I had different experiences”.
On an other note…
I’m actually worked/working on that. I’ve tried to add this as an option (decay rate, so you can increase or decrease the rotting speed (or prevent it completely) like the item spawn rate) in build version 0.C-7307 (no, I’m not kidding you), along with some other options.
However, when I’ve coded it up and tested it, the changes on food freezing hit and I had to redo most of it.
Then I went on a testing spree which took close to a year, and when I was ready to fix code collisions on github, the feature freeze for 0.E hit.
And now, when I finally could work on a pull request, I don’t have the time, since I’m stuck between running errands for my family (as I’m the only one without a precondition which would put me at the risk of dying for leaving the house), work which I’ve procrastinate to much about and a court case with someone from a different country who owes me money and wants to fight over it (or just delay it, who knows) 
…
Just wait a year or two and I’ll get there… maybe 
.
