They're trying to do two things.
Force an interpretation of the SC ruling that forces a corresponding change in the guidance.
Get a declaration that the Equality Act, as now interpreted by the SC, is incompatible with the HRA.
A declaration of incompatibility doesn't force HMG to do anything, but it's a signal they could get an adverse ECtHR decision later on (which also has no enforcement mechanism - see prisoner voting rights).
So Goodwin is still relevant and I can see why Croft could be too. Disapplying the GRA to the EA has taken away a lot of what was supposed to be a solution to the problems of those cases.