I think Hazlady is spot on ...
I think the raise in "the scapula plane" is based on new-er research .... I think I read about it in Scott Hogan's "Built From Broken" book & have been doing it that way since this past year, including when doing older dvds.
When Cathe started using the term "sumo", maybe 10+ years ago, I remember looking it up ... it can be used interchangeably with plie, however some do distinguish a plie as being a little further turned out as in ballet if your hips can manage - as Hazlady mentions.