I believe (correct me if I'm wrong) DU was removed on the basis that the hierarchy was consistently inactive and the regiment was failing to fulfil their purpose.
I agree in the sense that 442nd and DU perform the same role and for the most part this suggestion is just a model change. However, equipment did vary between the regiments. The current "special equipment" which 442nd recieves is quite frankly bland aswell or inoperable, like the republic turret and the rare ocassion where the TX-225 will be used. As well as the fact the 442nd is a "siege battalion" when we don't exactly siege anything.
It just makes more sense to have the regiment feel more accurate to it's actual job role, as it was just labelled "442nd" to make people feel as if it wasn't a DU knock off and like it was something new to the server.