Hm. This is a good point and you've made me think about this in more detail. (I'm a gay man myself, for context.)
Right. Let me try to explain what I mean. This might be a load of muddled nonsense but what the hell.
I think where I'm coming from is that in my head there is a distinction between infertility as cause (as in a medical condition, a diagnosis) and infertility as effect (as in the resulting situation).
Is 'infertile' a medical diagnosis, or is it the result of external circumstances? Is it both? I suppose the thrust of this particular argument will be about how the medical insurance company wants to define it vs. how the couple(s) attempt to define it.
Connected to that, I think what the article — and some of the people involved in this scenario — are doing is attempting to wrap surrogacy up as a 'treatment' for infertility. Is it? Isn't it? I don't know. Maybe in the US, where medical treatment is (largely) privatised and profit-driven, there's a different usage case than here in the UK.
Perhaps I've too quickly jumped to assuming the semantic usage of 'infertility' as primarily medical, and therefore the concept of situational infertility doesn't sit quite right if, technically, neither party is biologically infertile. In that context it feels a little clunky. (To be fair, we don't know if either of the guys in this case are biologically infertile, because the article doesn't say.)
However, I also understand what you're saying here and I hadn't considered that especially in legal and activism terms, there might be a broader usage of the term. Or at least, a strong argument for having one.