If it is the system launcher and that permission was provided automatically, all you need to do is use another launcher.

I am using stock android on a smartphone that was in the Android One program. I have not changed the the launcher.
My expectation when keeping the Google first party screen lock thing is for it to not make it easier for me to make the mistake of leaving the phone unlocked.

At this point, any app installed on a certified Android device in these regions must be registered by a verified developer.

And that will mean that if I were to feel like making my own app for the smallest of things and just install it on my own phone, I need to tell Google: "Hey! I am programming for Android!" as if they don't already have enough of my data.
And then sideloading would probably require signing it with a certificate, so Google will always know that I made a software and installed it on my phone.

There is no PR stunt here

Yes. There is no PR "stunt" here. Not everything that includes PR is a stunt.

Using the phrase "PR flavour text" refers to whatever PR is saying to make the actions of a company, seem less controversial. And that is the main job of a company's PR department.
In this case, it is:
'This change aims to reduce malware and scams associated with unverified apps, as sideloaded apps are significantly more likely to contain malicious software'

And yes, that thing is a lie as you already explained. That is why I call it PR flavour text.

2027 and beyond: We will continue to roll out these requirements globally.

This just gives me a deadline for switching to a Linux phone.
Seems to have come earlier than what I thought I would be able to manage, but I will have to manage somehow.