Yes that was exactly the point I was making in the other thread when I looked into how much they've played. Just like you alluded to, Slot has a core of players he trusts.I don't really know anything about the guy but the first thought that came to mind was that he's found himself in a situation that's almost too good to be true and he doesn't want / is scared to fuck it up.
That might explain why he appears to be reluctant to rotate and sticks to that small trusted group of players that have performed for him thus far.
But it's equally plausible that he just really doesn't rate the likes of Endo et al and Chiesa is useless and needs shipping back to Italy pronto.
I guess we'll (I'll) learn more about him as time passes.
The rest, like Endo, get about 5 min in the games that mean something, thats unless injuries force his hand.