Italian coaches are stubborn, no doubt about it. Just look at Capello, Del Neri, Mazzari... all stubborn. The only one that isn't is Ancelotti who can actually use several formations.
If Asamoah can play left-wing back, he can play left-back as well. There isn't much difference. People can't say he can play LWB but not LB, it's really the same position except that in one instance you have another player sitting behind you. He still tracks back to the end line and defends the wing like a LB, so it doesn't make any sense to not at least try him back there after this two year experiment.