Qwiss Gazza M I think the problems shown in that video with Kiwior not really knowing how to play left back are compounded by Havertz not really knowing his role yet either
I dunno, the guy implies Kiwior should be doing what White normally does overlapping on the right when Partey inverts. But he doesn't seem to understand that White makes those runs on the right flank because Saka and Øde do their thing on the right flank? Their specific traits and exchanges are what attract the defensive heat that makes White's overlapping decoy runs so valuable.
There's never going to be a similar Martinelli–Havertz thing and there never was with Xhaka either. Kiwior was probably told not to overlap, given that White was going for it every time he and Partey managed to switch, even before the subs were made, after which Zinchenko came on and we ended up with a situation more like last season.
More briefly, the issue's little to do with Kiwior, it's that an inverted right back won't work with the balance of our front four.