I think the problem is what I would consider to be the unnecessarily wide definition of "gender reassignment" in the EA itself.
s7(1) says: "A person has the protected characteristic of gender reassignment if the person is proposing to undergo, is undergoing or has undergone a process (or part of a process) for the purpose of reassigning the person's sex by changing physiological or other attributes of sex." [My bold for emphasis]
What exactly does "proposing to undergo, is undergoing or has undergone a process (or part of a process)" actually mean?
Could self-IDing as a gender opposite to one's biological sex be argued to be the first step in, or part of, the process of gender reassignment?
Parliament should have set a higher bar for what qualified as gender reassignment.