If we're thinking of music theory, why isn't the progression at [06:37] a descending diatonic (D C bmin amin) rather than (D C D C)?
Here is Tomo's comment:
"Thanks so much for subscribing to my Guitar Wisdom. Please watch the video a few times, and something will click for you! In this lesson, you can think of A- B- or C D. Try it both ways! You can use C and D Major triads or mix them with D, C, B-, A- (on Strings 123). The best way to learn is by not trying to get one answer too fast. Please enjoy the sound, and don't worry about finding one right answer!"
Nettle