Some, undoubtedly will test this law change. As the author of the article says, a letter from a physician will be required. So it is up to the physician as to the wording of their affidavit on what qualifies to them as a change of sex.
If someone wishes to change their BC while still having a penis... well, it is what it is. A penis. That's just speaking plainly. We're all (okay mostly) adults here.