This is so confusing to me.
I can see how it would be appropriate to socially consider someone with Sywer's as female, and it would seem unlikely that they would have any advantage in sports over XX women (although I would like some data on this). That's fine.
But the term 'XY female' - biologically speaking, how does this exist? The mutation or deletion of the SRY or other genes that result in Swyer's prevent the development of a male reproductive system; female reproductive structures form to variable useful degree in its place, but crucially there is an inability to produce gametes.
People with Swyer's have streak gonads, which are non-functional for producing either sperm or eggs. If they have a normal uterus they require egg donation for pregnancy. I believe they are also given hormones at puberty to help develop secondary sex characteristics and healthy bone mass, so presumably these have to be continued/altered during pregnancy. All this is because, if not for their gene mutation(s), they would have developed as male.
There are no healthy XY people that produce eggs; thus there is no disease that affects XY people such that they cannot produce eggs when they were on the developmental pathway to producing them - because that developmental pathway doesn't exist. Therefore 'XY female' is a colloquialism for people where it would seem strange or cruel socially to consider them men, but technically they are male, no?