The single-arm pullover amplifies core activation to the extreme. There's an anti-rotation and rotary stability component that isn't present during the bilateral or isolateral versions of the pullover.
Add in the leg raise hold as I have my NFL athlete Fernando Velasco doing in this video and you'll find this to be one of the most challenging core exercises there is. It's also an incredible movement for exposing and addressing imbalances throughout the kinetic chain.
You got the introduction to MRT last week, now here's the meat. If you've got limited time but want maximum results, this is your baby. The cool thing? The workouts won't take you much longer than 30 minutes.