Isn't Peacock's role more around issues like player welfare?
As for Sinfield, I think DoR is bascially code for "Head Coach, taking on some of the responsibilities Hetherington did". Hetherington is/was a lot more involved in player performance that other CEOs probably are at other clubs.
I suspect that there is probably also a bit of clever branding by Hetherington to protect Sinfield from the sort of issues that Cunningham has at St Helens. If it all goes pear-shaped, Sinfield is merely a "man upstairs"? Lowes isn't a popular appointment and it wouldn't be hard to move him on - and I suspect Jimmy knows that.