Well it only seems logical to me defrost...heat, defrost...cold. Definitely sounds more logical defrost...heat.
If instead of getting frost off ones window, one prefers to put cold dehumidified air on ones window to remove fog, then I would suggest using the duct position marked with the up arrow in some cars and a drost sign in others, bi-level in others.
Bosch Master, ASE Master, L1
33 years MB technician