I do believe now that they chose the aspect ratio first, and are now taking advantage of the extra performance in other places.
But this is a misguided and rather asinine decision to make. To add black bars to a 16:9 TV screen because when you play some movies on said TV that were meant to be played on a 2.40:1 movie screen, black bars obvisouly must appear... it's just ridiculous.
No one WANTS black bars on their TV when watching a movie. It's an aberration caused by the different screen formats. If TV's had screens that automagically grew wider to accommodate the aspect ratio of the content, EVERYONE would use that feature.
It's like saying: "Hey! I know! instead of having 7.1 surround sound, let's only have 2.1! Because people without 7.1 systems at home want to truly feel immersed by exactly replicating the inferior experience of listening to a movie on their speakers at home vs the sound system at a movie theater!"
Yeah, ok.
If everyone had 2.40:1 aspect ratio screens at home, this would make sense.