If the players feel they are regressing, and there's evidence to back that up, then it should be pointed out how unfit they all were under Ange (no idea if that's Nuno's fault), but it's a strong argument for change.
This, though, is bollux:
"the persistence in using Nicolas Dominguez as a left-sided midfielder despite the number of specialist wingers in the squad"
I'm reasonably confident that using Dom as a high quality pressing option against the top teams was successful. It was against weaker teams, or when he was supposed to support his fullback, that the experiment didn't work.
For all Ange’s faults, he didn’t have time to make them unfit. And I’m not massively sure they were, it’s a classic new manager thing to say how unfit they are and a dinosaur like Dyche was always going to like the ‘get running’ approach to training. Time may have better been spent on set pieces.
To be fair, Dyche went to great lengths to say he wasn't saying they were unfit just not the right fitness for his approach. (Whatever that means - presumably it's a balance between sprints and endurance?)
I would presume that under Nuno we were more prepared for sprints then recovery as we usually (with less possession) covered less ground than the opposition, and Dyche wanted us to cover more ground so upped the endurance training. If we (ie Marinakis/Edu) were serious about becoming a possession based team we would need to do that so Marinakis should have supported the extra training.
I'm pretty sure that the link between possession and distance works the other way round i.e. you run more when you don't have the ball than when you're making the ball do the work for you. I think high press v low block might be more akin to your line of thinking, but even then that's more about focusing the workload in a different part of the team than doing more work overall.