I can see both sides of shag basic - chugs being either considered a “move” or a “basic”. For me, they are right on the line.
It doesn’t help that defining a basic versus a move is a bit of a fuzzy difference as well. A basic is generally a short simple pattern that repeats and is generally seen as common foundational knowledge. There’s a bit of gradation here too, where a simple under arm turn could be considered a basic move aka “a basic turn” but is maybe not a “shag basic”.
For the chug to be more squarely in the “is a basic” category, work needed on how to teach and do this socially without it being a “big deal”.
Maintaining one of the Shag Rhythms and using the chug action to decorate the slows the would make it more of a “basic” and less of a move. Continually doing chugs pushes this more into move territory.
The arm dropping per Leading and Following Chugs makes it less normal to keep one of the standard Shag Rhythms and lends its self to repeating the motion and not doing quick quick, making it move of a move and less of a basic.