Unless messaging groups are pretty exclusive, the data is fairly easily to extract regardless.
I also have my doubts on the security of the computers involved.
Of course, assuming no complete literal invasion of our homes, might force them out of knowing everything.
And also, probably Facebook tracks quite a lot of behavior as to where you click, which Mastodon doesn't.
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!