I don’t use Big Sur but I don’t think it has any affect on logs. Without SIP, you could patch the kernel or something and change whatever you want, but that would of course be nuts.
I share your curiosity. If your computer isn't already managed, installing an MDM profile in order to view logs is ridiculous. I don’t even think there’s a way to do it without paying money.
That page is somewhat misleading. MDM is one way to install configuration profiles, but you can also install them by hand. No signing required, either. You can just stick that XML in a file with extension .mobileconfig, then double-click the file, and it will prompt you to install it.
Or download a signed version from here (not my site):
