There is a way to make some sense out of that, but you'd have to REALLY stretch things.
Let's say it's a 1911 pistol, the one we all know and love.
Now let's say it's chambered in .40 cal... not really common, but it's been done.
Now let's call it "Glock .40" instead of .40 S&W... which isn't accepted as proper, but
technically, you could make an argument for it considering the fact that while it's named the ".40 S&W", Glock was able to sneak their Model 22 on to the market
before Smith & Wesson was actually able to get their 4006 out there... effectively pulling the rug out from under them. The first pistol to the market that chambered the .40 S&W was a Glock pistol.
Yeah... kid at the cleaners was confused and/or under-educated, maybe trying to sound cool. But if I were forced to make up an elaborate reasoning... well, there it is!