Wawrinka could well be using RPM Blast,since his rackets are strung by P1,so this is theory one.
Besides that you can't say he is using RPM Blast,or neither querrey or anybody else until you know for sure.
How many black string are out there??
Tecnifibre Black Code(Tipsarevic and somebody else),Signum Pro Blackline Tornado,Signum Pro Black Hyperion, TopSpin Cyber Black,Cyber Twirl,Cyber Whirl and anything that finishes "irl",just to name a few.
It's only assumption,but as all ATP players don't test different strings or go to different companies they will probably be using RPM Blast because Nadal uses,it's Babolat and.....