I don't ever recall saying that, but if I did, I'm happy to have been wrong. Super stoked about the direction we're going.
The only thing to that effect I see right now is that responsive less files will no longer be separate from the core. That will probably mean that I will be forced to support mobile platforms.
Is there more to it?
(Aside, wishing someone would take a deeper look at https://github.com/twitter/bootstrap/issues/4935)
I currently have scenarios where I want the same version on the desktop and mobile. That's trivial because I simply don't include the responsive CSS file.
In 3.0 the media queries are part of the core. So I can't just leave the responsive CSS out. Further, it's mobile-first so things like the navbar would be collapsed by default on a mobile device. I would be forced to negate that to get an uncollapsed navbar on a mobile device (as desktop version).