The distinction is crimes committed during war time versus crimes committed during peace time. During war there is a break down of civil authority and general chaos. During the chaos crimes will be committed due to circumstance. During peace there is civil authority and general order.
Currently the extraordinary circumstance of war is absent and is not a mitigating factor which warrants a blanket pardon. This is also true in the 1974 pardon of Nixon.
Well, that’s an argument. But it fails the historical test of Carter’s pardon of draft dodgers and some other individual cases.