Good point.

Paul:

Valid point, but completely separating accessible content is also an accessibility reducer, IMHO.

An icon/text could be placed next to search results that emphasize the screenreader-friendly pages and even a ‘filter by…’ option to rank in the search results.

Another feature in the search results — and for every result?

Guess what interface clutter does? Reduces accessibility!

So, is this a good thing? Well, if you are blind, and depend on a screen
reader, then yes, this is a nice addition to your web surfing tool kit.

I think you’re taking the same shortcut as they do.

From their FAQ page:

Google Accessible Search looks at a number of signals by examining the HTML
markup found on a web page. It tends to favor pages that degrade
gracefully — pages with few visual distractions and pages that are likely
to render well with images turned off.

Currently we take into account several factors, including a given page’s
simplicity, how much visual imagery it carries and whether or not it’s
primary purpose is immediately viable with keyboard navigation.

Some of the basic recommendations on how to make a website more useable and
accessible include keeping Web pages easy to read, avoiding visual
clutter — especially extraneous content — and ensuring that the primary
purpose of the Web page is immediately accessible with full keyboard
navigation

IMHO, their tool/filter takes into consideration many more issues than just sight impairment.
I think the “problem” is that they made a too narrow claim