In my experience, a solid back line is an absolute prerequisite to employing a high defending style. No matter how good the high defending is, it always results in moments of intense pressure on the back four. IMO, it's a very high risk approach that is only made doable by having a solid to very good back line.
It can always work against weak opponents but we need to prepare to for strong opponents who can handle high pressure with composure. I mean, Mexico tried to use high pressure against us and, in the GB era, we became good enough to beat that pressure regularly, often leading to multiple scoring chances. And we're nowhere near as good as many potential opponents are at handling that kind of high pressure.
My issue with Gio is that he can be a net big asset when he doesn't have a lot of defensive responsibility. No matter how good his work rate is, his relative lack of pace is the problem a coach must account for. For him to be at his most effective for us, he needs to play a certain role that focuses on attacking creativity with a zonal defensive responsibilities only, because that doesn't require him to cover a lot of ground which will never be his forte.
IMO, that role for Gio is only possible with a strong defensive back line. GB tried to play him at wing mid in that last game, with typical defensive responsibilities and that burned out Gio very quickly and often took him away from where he needed to be to quickly facilitate the attack. And he was not highly effective on defense, adding pressure to our weak back line. A lose-lose situation for us.