If Alice wrote on Bob's wall, it should be a part of both Alice's and Bob's takeout. Similarly, if I am tagged in a photo, it should be a part of my takeout. Imagine if my email provider (Google Gmail) said you can only takeout the emails in your sent folder.
In fact, I'd argue if Alice has made their contact information (email, phone number, physical address) visible to Bob, it should be a part of Bob's takeout. Including Alice's location history (provided Alice shared it with Bob) would probably be pushing it a little but only because it becomes difficult to argue for people with whom too many people share data with but anything that Bob is explicitly and manually tagged and is visible to Bob on Facebook in should definitely be a part of Bob's download.
Facebook can't have it both ways: you can't make it easy (by default) to share and still use the data as a moat.