You've got to be kidding, Mac....Rhythm and blues playing guitarists have been using double stops since the cows came home... Recall a fellow named Chuck Berry, then check memory cells for a Texan named Johny Winter, and most blues guitarists of our generation including, Clapton, Duane Allman, all the Kings, Hendrix, and Stevie Ray Vaughn, and most slide players as well. Learning those by ear as a staple set of riffs, in any key has been a required right of passage for any aspiring blues player attempting to play like these icons. Listen at 1:34 of so and hear such a staple... And I don't think he spent much time with your friend George... though I must admit, I was stunned to realize that Steve Vai was not the creator of the first seven string guitar!
https://www.youtube.com/watch?v=Wp1i4TrWBjM