my vet gave entirely different reasons for it.
one being they find it nice (yep not our cup of tea)
that they get nutrient from it
its not just in dogs, many young animals eat their parents to get their microflora for normal digestion.
although not an apealing habit though
the change of diet can make the difference although some like my sisters dog is still at it and now 6 their solution is fast with the pooper scoop