This is idiotic, tbh. I was a goalkeeper for twelve years and I was always worse than other two goalkeepers when they compared our fitness, speed... mostly because I'm 6ft 7inches tall, but I always performed better at games because the other two were lacking decision making, determination, positioning, etc. If that's how the squad is picked, then it's poor man management. Benitez should know that manager at his level is mostly motivator, psychologist and tactician and not some professor from middle school who thinks that ones who know subject by heart are better than ones who truly understand it.
Think it's pretty obvious it's not as simple as "who runs the most plays". There'll be a shit load of things they follow and combine that with what they see.