I have read the article, the book, seen him in person, got instruction from a one plane instructor, etc....
Understand this, ben hogan who is classic one planer according to hardy himself, has a very "two plane" address, Tiger. Ernie, VJ etc..... are "one plane swingers" set up very two planeish. and yes randaom, your right shoulder should drop to the inside on the down swing, that feeling you describe is fine. the shoulder plane is flatter on the way back and steeper on the way down