No idea, I guess it's just manufacturer's way of helping some advanced styrene nutcases out there in whatever small way they can, while not really spending that much extra to make the parts. The same can be asked about many of the parts from the new Dragon M1A1, with multi-part exhaust vent doors in the back, then separately molded engine cover panel (this time with the mesh piece linked together with the panel, which was traditionally done wrong by italeri and tamiya..). if one isn't a scratch builder, those features are definitely a why bother as well.