I used to call it the 'Game Boy Advanced' and 'Advanced Wars'. The reason is there are already nouns in both and the 'advance' is clearly being descriptive so people naturally use the adjective which is 'advanced'. 'Advance' is grammatically correct but in GBA it means the thing is an 'Advance' not a Game Boy; and in AW, it means 'to further wars' rather than the 'wars with advanced technology' that I think they were going for.
As for why it's being released? Probably because it's finished and needs to start making money at some point. Plus, it doesn't seem like the backlash they expected is going to happen. If anything, some people might even enjoy it more.
Nintendo is all over the place with pricing. Isn't metroid $40 and this is $50? And then the new Zelda is $70 but botw is still $60 and it's the oldest game.