Re: aspect-ratio property

I thought that CSS re-flowed constantly while data was being loaded. I
had assumed that it would see the start of an element, create the
node, apply  the CSS, download the content of the element applying it
as it goes, then close the element and could then re-draw?

(I'm not yet far through the article about how browsers work and don't
know if it covers the process in that much detail)