Fediverse instances can also do most of this.

Do you have reason to believe any of that is happening?

You could de-anonymize many users with those

Bruh your Facebook username is literally my first and last name. Same goes for most people on most platforms. I don’t particularly care about anonymity.

Any fediverse apps could also get access to contacts or other locally-stored info on your phone.

I’ve never used a Fediverse app that asked for any of that. They have no use for it.

“But I wouldn’t use that app.” Well then you wouldn’t be someone using Facebook either.

You don’t seem to understand the myriad of data that Facebook collects unnecessarily and without user consent. Do a search for Facebook Pixels. They were just caught decrypting traffic from SnapChat. Most Fediverse servers are far too small to even bother with collecting and selling that sort of data.

The two are not even remotely comparable.