This answers why there's a message on my Mac in Sonoma 14.1.1 saying my own account (personal use, not restricted by anyone else) has changes "restricted by a profile."
What doesn't make any sense is why my iPhone has locked down my Mac's Apple ID simply because I'm sharing data across all devices.
I use a time-tracking app that will track usage across all my devices and consolidate that into its summary to see where my time is spent in much granular ways than what Apple provides. That requires Sharing Across Devices to be on.
Having my iOS devices lock down access to my account on my Mac makes no sense. I don't think this has been thought through. (I never would've guessed it was my iPhone that was the "profile," if you can even call it that, that caused the restriction, based on its cryptic message.)