Yes he is. For most of his career he's been a cb but recently when Germany started playing with 4 cbs before they switched back to fullbacks he did play out wide. Belgium did this too but you wouldn't call Vertonghen and Alderweireld fullbacks. They just so happened to be better than any Belgium fullbacks while Kompany and Vermaalen started as cbs.No hes not.
Played loads at Left back and right back and both centre back positions.