The "CSS pixel" is just a pixel, unscaled for high-dpi displays. The point is to avoid revealing the hardware while allowing a bigger starting amount for a bigger window. If you prefer, just pretend I wrote "32 MiB".

Human time is valuable. That is the whole point of this. My time is wasted when my computer gets so slow that it takes 10 seconds for the Caps Lock light to respond. My time is wasted when the mouse lag is so awful that it takes me half an hour to kill a few tasks. My time is wasted when I have to walk away from an unusable computer, checking back every few hours to see if the OS might have killed the biggest task.

Web browser resource consumption is why I have a fresh new HN account. I had to power cycle the computer today, and it seems that Chromium won't save passwords over a restart unless I upload them all to Google.