Looking at the comment in the actual code change:

"If we are being asked to delete a system app for just one user set flag so it disables rather than reverting to system version of the app."

... Joy. This makes the 'nondisable' list an even more unhinged malware delivery mechanism for operators, because you won't be able to disable the carrier shitware app and it gets updates!

It's time to start cracking down on malware preloads on phones and the over-subsidization of consumer products. We need to stop accepting $50 smartphones and $100 smart TVs that are crammed with a few hundred dollars of profit for the manufacturer to shove ads and malware at you nonstop out of the box.