It seems more like a fad or trend to me but the main difference is meant to be that a Head Coach focuses solely on the football side whereas a Manager would get involved in all the other aspects of running a football operation such as training facilities etc.
But Tony repeatedly said for both PW and MT that he would be the facilitator and give his Managers what they needed to concentrate on the football aspect of the business so there’s no change except in job titles really.
Maybe it’s a way of starting the restructuring which RS hinted at. Probably involves TS taking a step back and leave a Director of Football to do what he did before. Will he be able to step back though