Difference of opinion, Matt.
I see a catcher with excellent awareness and positioning. He put his heels on the 1B line before catching the ball so he wouldn't have to spin after the catch and so he could track runner's progress with peripheral vision.
Once he caught the ball, his simplest option was to reach out and make the tag. His next simplest option was to drop to his knees and put his mitt on the front edge of the plate. Instead, he tucked the glove into his gut like a fullback, lowered his shoulder, took a decisive step, and slammed into the runner above his waist. His actions pretty clearly line up with the discussion in this year's book.
I have to agree with Swamp... the catcher lowered his shoulder while the runner was attempting to slide.. Everyone that comes out of the dugout gets ejected...