I'm sure flyover is vastly more qualified to advise people on this topic than I am.
I think the boot glove is an application of his layering principle. For proper bootfitting it's not possible to add extra layers inside. So the boot glove adds a layer outside plus provides a insulation barrier when boots are in/under the snow.
Season length: 21 months, Nov. 29, 2010 - July 2, 2012
Days in one year: 80 from Nov. 29, 2010 - Nov. 17, 2011
Season vertical: 1,323K in 2016-17
Season powder: 291K in 2011-12