Yes there absolutely are circumstances where services need to be single sex and these should be protected and single sex.
And one of the basic circumstances might include where the service provider is a woman working alone. For any service. It may be that a woman is only comfortable, for her own safety, offering the service to women.
In any sort of larger organisation, clearly the organisation has the ability to arrange providers to support both such women and clients.
But for a sole service provider, the rights of the provider can outweigh the needs of clients to not be "discriminated against". A sole provider is not doing to be dominating the market, so clients are not going to be significantly impacted by having that provider not cater to them.
I believe this principle is not generally controversial in this sort of legislation - balancing the rights of clients versus providers, depending on provider size.