It seems to be something with mostly American companies. EBMM has followed suit with the SBMM line. Gibson & Epiphone, & Tobias. Certain other companies choose to keep their name on the bass, but designate it with a different series. Lakland Skyline, Sadowsky Metro, Spector Legend/Euro, Warwick Rockbass/Pro. Ibanez follows that model with the Gio lineup, and even their Premium/Prestige to denote upper end lines.Could be true, but why isn't that the case for Ibanez and the others? Most people who play long enough to get to the point of upgrade are already familiar with the differences between the models, and already know that the true upgrade comes from the MIA. But you very well may be right.
There's no real wrong way to do it but you can get an idea as to why Fender caters to the brand labelling just by looking at those on here who sneer at Squiers and are devout Fender MIA fanatics.