When they are talking about modal progressions they are talking about progressions that were written to sound good when a particular mode is played over them. If a progression is considered A Dorian it would resolve to A minor instead of G Major. A Dorian is the 2nd mode of G Major but for the progression to be Dorian A Minor would be the root chord. There are a bunch of examples of modal progressions on the internet.

Chris Davies it simply means it resolves to the ii chord instead of the I. Dorian mode and the ii-V-I chord progression are very common for funk

Backing Music Audio Track?

He says very clearly towards the beginning of the video that the 2 high strings on his guitar are tuned differently than standard tuning, so he'll be on different frets.

a valid point. however, ironically, the point in tuning to all 4ths is to remove unnecessary complication. Tom typically teaches intermediate to advanced lessons; at the point when one is studying this type of material, it's vital to listen with your ears rather than the eyes. still tho, it can be weird to see if you're in standard.

These are not lessons for beginners (if that's what you mean with "youngsters") and I don't see the problem. He actually explains how you can play it in regular tuning.

he usually tunes standard for lessons