Perhaps if you thought that one unit couldn't withstand a counter attack but two could and wanted to see the defensive dice?
Anyway, the plausibility of the scenario is kinda irrelevant. Are you really allowed to load units in combat movement, offload only one of them, then offload the other in NCM? Is there a restriction that it has to be to the same territory or is the rule about transports having to offload to the same territory not in revised?
Revised-OOB is a strange ruleset, IMHO, with some aspects coded even more confusing in v2-OOB. Revised-LHTR starts to sort things clearer and from Anniversary onwards the rules are structured pretty good, as I think.