No researcher will request or get access to "5 million Facebook logins" through the DSA, since such a request wouldn't comply with the DSA requirements, so your point is moot. In fact, we live in a quite different world than you imagine. Currently, researchers don't even have access to the public data, as the article points out. When it comes to private data, researchers won't get access to private messages either, but rather to aggregate-level privacy-preserving data (assuming that the DSA isn't killed before any of this happens by the industry and Republicans, which you seem to advocate for).