Yeah but the 3 at the back gets the fullbacks further up the pitch and for me makes better use of Dier's unique skillset. It beats the opposing midfield by stretching it out rather than flooding it.
Davies is more of a proper fullback than the more versatile Rose, but with the way Trippier dominated as a wingback for England I feel like that's the stronger formation for us going forward.
It also asks a little less energy-wise of Dembele.
The downside of course is then you can't play all of Kane, Alli, Eriksen, and Son, a foursome that is sometimes just completely unplayable. Unless you drop Eriksen deeper of course, though he hasn't seemed his best the couple of times I've seen him deployed there.