The main difference I've read is there seems to be more ability for Dak to alter a play at the line — a check-with-me aspect based on the defensive alignment. In the Garrett/Moore scheme, the receivers had route options based on the alignment of the defense. I think McCarthy wants to essentially eliminate the options so the receiver doesn't zig when Dak expects him to zag. For example, let's say the called play has Lamb running a curl, but Prescott notices when he comes to the line that Lamb is one-on-one with the corner with no safety help and the corner is playing press. Dak then checks Lamb into a go.
This is different than checking from a pass to a run or vice versa or even checking from one pass play to another. It's altering individual responsibilities within a play. (Romo did some of that when they tamped down Garrett's role and made the offense more "Romo-friendly." He would motion for a receiver to run a specific route based on the defensive alignment. However, that control was somewhat limited by the scheme/philosophy.)
I could be wrong, but that's how I understand it. If that's the case, I do like taking the guesswork out for the receivers. If the defensive alignment is right, they just run the prescribed route. If it is wrong, then the route(s) get switched by the quarterback. Obviously, there can be miscommunication or the QB might read the defense wrong, but it should limit route mistakes.
Some coordinators believe that the receivers and quarterback should both read the defense and adjust because that creates more flexibility for getting open, but that also leads to more mistakes if they aren't on the same page. Others believe in giving more control to the QB to move the pieces around if they believe that QB has the ability to properly read the defensive alignment. Less options mean fewer mistakes, but if the QB reads it wrong, it also means the WR won't be open because he's going to run right into the coverage.
