Earlier quoted context omitted.
It's not nonsense. Meta will have a shadow profile of pretty much everyone, wherever the person in question is blocking their trackers or not. It's still a good idea to block them, because it will reduce the amount of information they'll have about you, making their shadow profile less useful Nonetheless, Meta knows you exist and will almost certainly be able to tell some things about you
"What can I do, under US law, to minimize what they store about me and my behavior, or at least keep tabs on them?" "...Nothing" "Nonsense, and the article addresses this. 'Block Meta’s Trackers' The parent said nothing could be done. I say that's nonsense and listed a thing that could be done. You respond it's not nonsense and then list the same thing I mentioned. I am very confused by your thought process.
I'll be honest, when I read the initial comment I interpreted his question to be closer to
"stop Meta from collecting my data to a meaningful degree"
vs how you've interpreted it -
"reduce the amount of data Meta tracks even if only marginally"
That's why the response saying "nothing" made sense to me, because blocking the trackers only has such a minor effect on Metas tracking.