To me, this would be Facebook taking advantage of their stronghold on the market to continue to dominate the market.
Let's remember this is not Facebook's data, this is their users' data. It should be up to the User who they can share their data with, but they weren't given the choice to use their data with an app because Facebook decided they didn't like the way the other business competes with them in some aspect or how they aren't making money out of the third party app. An example is Facebook won't grant Influencer Marketing Companies access to their API even though the user (The Influencer) wants them to have the data so they can get paid based on the views, shares, comments, and likes of the posts they've been contracted for. User has a legit desire to share that data to the point where they will take screenshots, GDPR deletions, etc to fulfil the need for that data to be shared. Facebook's reason for not allowing them access is simple, they don't make any money out of the deal.
So if they refuse to allow you to share your data with people you want to share it with, that is bad. Sharing your data with companies you don't want to share with is also bad.