Stones/Lewis can do the role of moving into midfield on the right, but neither of our current left footers (Aké/Laporte) can really do it on the left. The angles etc are different for left footers rather than right footers who can do the LCB position. Gvardiol definitely has the skill and talent to do it, which alone increases our flexibility and reduces reliance on an injury prone (but immense) Stones. Aside from that, he defends like Dias, can pass like Laporte and started off as a midfielder. Pretty much ideal for Pep