Why, so that when people criticise, for example, poor media playback capabilities we can claim it's an unjustified criticism because they're not N-series devices?

Different designations don't get away from the fact that many of the stock applications on the N900 are lacking basic functionality, in particular Modest and Nokia Messaging which are currently being ignored in b.m.o. For heavens sake, Modest doesn't even do what my N85 used to do with ease!