Have to agree with Jack Daw on this one. I see no evidence on any of those pipers that their plaids are doing anything other than hanging straight down. There are no indications of the "drape" that you would necessarily get from the garment being attached somewhere in addition to the shoulder.

EDITED TO ADD: When you compare this guy...



...to Matt's half-belted plaid...



...you will notice that the top plaid is fringed at the bottom, while on Matt's, this is actually a fold where the cloth drapes. Completely different animals.