I'll leave the rest of your post as is. Opinions, etc.
The bold-faced? I'd love you to explain.
I think you're wrong.
Look at the stats surrounding injuries, particularly hamstring injuries, this season. And think about how much football international players have played the last few years. Udogie, Romero, VdV, Richarlison, Davies, all players with muscular injuries, most hamstring, and all regular international players whose game loads have increased. Look across the league at the hamstrings that are going (Saka's being the latest after a few warnings). And think about the minutes in these players for several years.
When people say we need to change our style of football because of the hamstring injuries we get, it feels so backwards. You surely give the football side of a club every support and tool necessary to play the game they play. Better squad depth, better physios/conditioning, lighten the load on players across the board (PFA where are you?)...that is unless you would be happy being near the top of the table playing like Forest, again, that's a matter of choice I suppose.
Does the manager have a bearing on things? Of course. His football is generally built on high intensities. But I think you're wrong to say the squad injuries are largely on him.