It's one of the stepping stone front office jobs for players to transition to management.
I won't pretend to have a pulse on who every teams player development coaches are, but Guerin filled that role in Pittsburgh between 2011 and 2014, and I can't think of anyone Pittsburgh developed in that time, and then he still got promoted. I'm just not convinced having skilled former players there matters.
I could be wrong, but for me, I don't expect player development coaches to take a third liner and make him a first liner, I expect them to help players get better at the "behind the scenes" stuff. Teaching them the little things it takes to succeed in the NHL. Lots of skilled prospects come through and don't stick because they can't win board battles, they can't play positionally sound hockey, they got by on natural talent for so long, they need to be programmed to play an NHL game now.
I don't think having a Patrick Kane instead of Darby Hendrickson as a player development coach would turn someone like Milne into a Guentzel, for example. So what does it matter if it's a grinder or a superstar. Just my 2 cents.