I can't speak for Google, and must emphasise that these are personal opinions. However I'd say that this entire marketing push is mostly for the super-engaged early adopters, not targeted at the general public. Looking at the YouTube videos, the more they seem to be targeted towards a general audience the less they mention these specifics. So, I suspect that the Ultra/Pro/Nano branding will mostly be used on the advanced Bard product that they speak about in the launch blog post, and on the APIs available to developers.