So lets flip the debate around do those longhaul pilots who wish to go short haul feel that they are suitably qualified for a DEC on something smaller that say does a 4 sector day into demanding european airports or Greek or Egyptian. That have very little or no ATC and a very "hooky" looking Vor/DME that threads you through the hills at 4am??? If the answer is yes then we are then saying that long haul is the pinacle of aviation experience !!! It equips you to fly anything.
However if we are saying no, you would need say 6 months RHS to get used to the 4 sectors and the problems we face in europe, then it would seem that both long and short haul have mutually transferable skills that need focussing on the relevant type of flying be it long haul and short haul.
Now surely command is all about aircraft management skills and nothing to do with being a "stick and rudder man/woman". These things have autopilots and personally i encourage my right seater to keep that in as long as humanly possible, stops the coffee being spilt.
So the story about the ATR captain swapping, surely a good captain is a good captain ie a good manager. There are a lot of not so great guys with lots of experience running around. So IMHO a good skipper on an ATR making close decisions getting into a Sligo on a windy day will make the same good decisions landing the 777 into miami on wet and windy day. Now maybe airlines put people DEC heavy who they have noted as good captains, who have made command decisions.
Who would you rather have in your left seat on the 777 a guy who has 10 years jet command say on a A320 who has made the decisions for 10 years flying with say an F/O with 5years on 777 who can fly. Or a Guy with 6 years F/O experience and no Command experience ?? Sometimes the hardest decision a captain has to make ist to tell the company that he/she is not taking the aircraft out no matter what the commercial pressure.. That ability comes with experience and confidence in your command experience..
Maybe that confidence is why some operators take DEC's on wide body after all the weight of the aircraft is just a number.