More like the alloy that SP cut the threads into is made of monkey pooMost likely as it uses the old SP threads and they suck monkey nuts!
It looks like a shim or spacer, I found on a Mini that when you tread the feedneck all the way home it didn't sit so the clamp was at a regular angle to the gun, no big issue. When I backed it out a bit so it would, even with loctite it would come loose again. So I screwed it all the way in and loctited it, no problem.