That's just a cya on Ruger's part. If you shot a lot of 40's and didn't clean the cylinders then loaded up 10mm's, it could potentially cause a problem. No different than shooting 38SP in a 357 mag.
I have a lcp that's more accurate than it should be for such a tiny gun. It rides in a J&J wallet holster for maximum concealment or if it's going to be a long day.
My super discreet carry is a lcp in a wallet holster. Otherwise it's a hellcat iwb. I'm an old fart. I wear jeans and a loose t-shirt with a ball cap. No firearm related logos. I just don't stand out.