"and don't do screens for the last few hours before bed" because that will help you fall asleep more quickly? or because that will help you sleep later in the morning 6 or 7 hours later? People never seem to mention that key aspect.

I believe it's much to do with blue light emitted by screens:

https://pmc.ncbi.nlm.nih.gov/articles/PMC9424753/

For me most things I do on a screen are fairly mentally stimulating (like video games), and even the ones that aren't (like watching a movie) inhibit the feeling of sleepiness I get when I abstain. So, it's better for falling asleep quickly.