Medic1210,
The clip seems to pull tighter on the brown threads of my blue jeans pocket. There was a time when either the 921 or the 730CFHS was all I carried and my pockets started wearing quickly in that time (despite not doing so with a year of the 710 and regular 730 and a few years of Cold Steel folders in my right pocket). At first, I thought it was the 730CFHS, but I've noticed the 921's clip catching tighter when I retrieve it. Maybe it's because I already damaged the pants and just the tighter clip is noticed.
That said, it's still such a wonderful pocketknife for everyday use (assuming you're not working on drywall without access to power tools).