No advertising agency sells your data. That would destroy all their competitive advantage. They sell access to the people they have data on. Regardless, it's irrelevant because the App Store labels aren't about selling the data, but about what is collected. (or supposed to be, as claimed by Apple)

They don't sell data, they sell access to fine grained slices of their users.

"You want to advertise to 65 year old white people[1] in QAnon so you can pedal a very specific kind of fear? No problem."

"You want to buy access to black women under 30? We gotcha!"

That is what Facebook does which Apple doesn't.

[1] I know FB doesn't actually allow targeting based on race anymore. They do allow targeting based on interests though which can easily amount to the same thing.

They all pay to "share" data through data brokers in order to get more info about you. It's the same thing.

Facebook buys data from data brokers, but does not share data with data brokers.

Do you work for them? The way data brokers work, from what I understand, is that it's a 2 way agreement. You only get the data if you give data.

That's not how it works, they accept money.

Can any app on AppStore avoid declaring those flags if they say in their marketing that they don't sell it? Or why does it matter for Apple and not for them?

Data used to track you is gathered separately from data linked to you.

A government agency can still order them to hand over all data they have, they are still a single point of failure from a privacy point of view.

I think that's fair, but is certainly a different concern than what facebook is doing.

It is debatable what that data includes but even if true it isn’t what these labels are about. The list shows purposes and types of data and Facebook declares they use all that data for the purposes of tracking, advertising and analytics.