You are correct that the ball doesn't have to touch the glove to be an error. Otherwise, when an infielder lifts up too early on an easy ground ball which rolls between the infielder's legs but doesn't touch the glove would have to be ruled a hit. The standard is whether the ball should have been caught with reasonable effort. In my opinion, Cespedes' play was clearly an error. Lorenzo Cain would have made that look like a deep but routine fly ball.
I'm glad it happened though. Go Royals.
But even if it had been called an error, Escobar would have scored, but it wouldn't have been an inside the parker. But I'm not sure how they would have called it then.