Sequencing for runways 22l and 27 is actually based more on inbound fixes, not types. There are some times when certain a/c will request something else, but not that often. Even landing 22l to hold short of 27 is a considerable distance and most a/c can do it. More often than not, a heavy given full length on 22L will STILL exit the rwy before 27.
As for splitting the arrivals based on cargo vs passenger, absolutely not. That simply is not a factor. Must've been a coincidence when you were listening, maybe very late at night when a fair # of cargo planes are coming in?