I used to set this pref to a higher value in ESR 91 and before (eg. 3000 or 4000 ms), so that I could allow more of a page to download prior to rendering. Now as of ESR 102, something seems to have changed, and items on a page load straight away. Now on some sites, the setting is respected and works, but on other sites, the page starts rendering immediately, before it has completely downloaded.

I have tried defeating lazy load for images in about:config. No visible change though. I find when I load the top level page of a site, the browser waits to render the page as desired. Any other links on the page though load immediately. even when it's cached, there's a "flash" and the page loads. Before on ESR 91, the screen would switch seamlessly.

Canadian Flyers is the best example of an "offending" site. When you click on one of the grocery store icons on the right, the current flyers images start displaying right away while they are downloading. If I have the nnglayout.initialpaint.delay set to 4000, I shouldn't see anything for four seconds. And upon cached readings, I shouldn't see a blink and a quick display. I should see the page show up as quickly as possible, without blinking.

Also try msfn.org/board. The first page may load as desired, but go to the forum sub topics. They blink and start painting right away.

Now for contrast, here are a couple of sites that renders EXACTLY the way I want it to. On first load, the page, and all of the links load only when they are fully downloaded (as long as it's within four seconds), and upon revisiting a cached paged, it loads almost immediately, and with no "blink" or "flash". The first page doesn't clear before the next one loads. The pages just seamlessly switch.

Ontario Highways - The History of the King's Highways and other Ontario Provincial Highways
RyanVM.net Discussion Board - Index page

I know, they're older sites, but these show what my objective is a bit more clearly.

Thanks for everyone's help.