As I understand it, it's not uncommon to want a sort of "deluxe" package where an egg from one parent is implanted in the other.
This is totally unnecessary, and potentially risky, but as this site says
The biggest benefit of reciprocal IVF for lesbian couples is to enrich their experience building a family. It gives each woman the opportunity to contribute to the conception and birth of the couple’s child.
Lesbian couples have undergone dual reciprocal IVF at the same time, so each woman carried her partner’s child simultaneously. Other couples have undergone the entire process once and then reversed roles to have a second child.
I'm not sure this is really beneficial to anyone. I can see why private providers might want to do it - it's money for procedures.
Is the point of this case to try to get the NHS to pay for it?