I noticed the same issue just a few days into having the Pencil and IPad Pro, and have only had it for a week and 2 days now. The Apple Pencil (2nd Generation) is worn, revealing what appears as black dots, initially causing me to think something was burning, but upon close inspection seems to be revealing the shiny magnet underneath, and has simultaneously worn into the outer edge of the IPad, causing permanent cosmetic damage.
I went to the Apple store near me yesterday to show the damage, and was initially told my iPad and pencil would be replaced, then upon the return of the employees, having spoken with their “engineer”, was rescinded the replacement offer, and was asked if I carried the iPad in a bag that might contain metal particles that might have caught the magnet, causing friction and wear. This is not at all my case, having babied this a machine from day 1, their assessment and backing out on their offer to blame me for a weeks wear has left me feeling very unsatisfied, and intend to follow up.
Previous to my visit there, I had not looked up this issue to see if it was a common occurrence, but I am seeing it quite frequently on various forums now.