This seems to me like punishing users (in this case web developers) for the mistakes of standards organizations of the past (W3C).
HTML is what it is and it's not going anywhere. AMP is not a solution to anything, because the whole world isn't going to adopt it.
A real solution is to write your HTML rendering engine to eliminate behaviors you don't like. If you don't want repainting/reflowing of the page when the img dimensions aren't known then don't start rendering until you know them.
But browser vendors aren't going to do that because users DO prefer reflow/repaint over waiting for the page to load. So this is a silly argument.
If they handn't fooled around with XHTML set of standards, we could probably already have something like XAML on the browser, with its GPU backend.
Alas, what we have is a Frankenstein stack, which when one does the magic incantations of HTML and CSS, maybe just maybe if the browser and corresponding version are the right ones, those transformations will land on the GPU.
given that AMP has no explicit browser implementation right now, but is just some guidelines and JS, implemented on top of the "mistaken" standards: web developers already can write pages conforming to the goals AMP tries to enforce, but too many of them didn't.
Stricter browser engines would punish devs more, to avoid punishing devs with AMP?
I'm not a big fan of AMP, but I'm not sure if intentionally worsening browsers for unliked but valid markup would be better. Users will leave a browser doing so.
HTML is what it is and it's not going anywhere. AMP is not a solution to anything, because the whole world isn't going to adopt it.
A real solution is to write your HTML rendering engine to eliminate behaviors you don't like. If you don't want repainting/reflowing of the page when the img dimensions aren't known then don't start rendering until you know them.
But browser vendors aren't going to do that because users DO prefer reflow/repaint over waiting for the page to load. So this is a silly argument.