If you do it like this, I guess your phone is not rooted. You can check and change build.prop for example with kernel adiutor. There are two lines called ro.build.version.security_patch (for me with Mi 9 it's 2019-11-01) and ro.build.version.security_patch_real (2020-01-01). I tried to change it, but it changes back.I simply checked for new updates, downloaded and installed. Phone rebooed into recovery, did the dirty flash, and rebooted back to normal. I always do the update like that.
Honestly, not sure how I would go about editing build.prop. I'll download the update to a computer and look through the zip file.
But I still don't know what difference would that make. Does it control the security patch version I see in my settings? My phone already says the security patch is at 2020-01-01 although the company system sees it as 2019-11-01.
In how many places is this setting stored?