For years port 80's sole purpose has been to forward browsers that started with http over to https. Now browsers don't even do that any more. There is no purpose for http on port 80 outside listening on localhost for ssh-forwarded connections to local web applications like phpmyadmin that you don't want to expose to the wider internet.
So port 80 has no purpose.
From the page you referenced:
So the 443 test uses software no one outside Google and other enterprise users have. So.... for the vast majority of the internet it's useless. Which you very well know.
In the wider scheme, what is troubling is:
The internet moves to https on 443, LetsEncrypt response = port 80 requirement
The internet moves to QUIC on UDP, LetsEncrypt response = port 443 TCP TLS requirement
Letsencrypt could move TODAY to lead with https on 443 for http-01. That makes sense.
What is hard about that?