All of mine are tight and most all are extended out to near max in terms of the LOP adjustment range and I have seen/installed/used dozens of them over the last several years and none had the kind of "play" in them you are talking about. In fact, the adjustable components in every PRS I have been around have been pretty tight even at the max of their adjustment ranges.
If you are getting that much wiggle/rattle from the buttplate assembly, try disassembling the stock and putting it all back together again and ensuring that everything is tight and otherwise as it should be throughout. If you don't want to go all in with the complete disassembly, you can start by tightening up the allen key screws throughout the buttstock assembly (the ones holding the sling attachment plates in place x4, as well as the cross-bolt found below and forward of the comb adjustment wheel on the left side of the stock). If that doesn't get it done (the dis-/re-assembly and bolt tightening)...and if you aren't actually needing to run the adjustment in/out...try a bead of silicon rubber around the junction of the rods where they insert into the stock body and see if that'll get it done.