I think it was to align the larger platform with the more advanced BCM50, and it gave two clear choices, the 200/400/1000's we're originally operated with Win NT, this was later replaced by a Linux build when they launched the BCM50, in the end the BCM450 was a lot faster and efficient than the BCM50 making that look sluggish, by Rls5.0 they had aligned the software builds, doing away with the sometimes confusing differing releases.
Shame really, the system could of gone on to do a lot more, bit of a shame they never phased out the old Norstar template they we're working from, I think this held it back.