So what difference would it make? After all, this is the result after AMP has done all its cleaning, which would give you a pretty accurate measure for page weight. What remains is the actual content of the page. It's the cruft that should be penalized, not the actual content.
Exactly what my sibling comment said, it's the publisher (presumably a human) who does the cleaning. It's not as easy to get a bot to clean things up and then measure weight, and the various "Readability" views aren't always correct (they're using heuristics).
Sounds like a publisher-assisted "readability view" would solve both problems, though. It would allow the user to view a "lighter" version of the page and search engines could just measure how large the "non-light" version is and penalize accordingly. I'm afraid that would incentivize the publisher to put ads and other crap in the "light" view, though.
