I agree it seemed a bit unlikely for a 17 year old intersex girl not to be aware of her condition - especially as a swimmer in training for the Olympics! I'm no expert but it feels like she would have had quite a few medical check ups in the lead up to that.
The set up was very much a last minute twist, but overall I was surprised and impressed by the inclusion of the intersex character in the narrative. Time and again we've seen intersex issues and language co-opted by the gender identity brigade, to the extent where I think a lot of people honestly aren't sure what the difference is.
I didn't expect that the show would come down so firmly on the differences. They make it really clear that although Piper tests for a higher testestorone level, her body doesn't absorb this testestorone and so she reaps none of the benefits - unlike the transwoman character Sadie.
Maybe it was just me, but I also felt the narrative treated Piper with more sympathy. The court felt quite rehearsed in its attitude to Sadie. Everyone was afraid of putting a foot wrong, everyone felt there was some way in which they "should" be behaving - some script they ought to be following - but they didn't really know why. It wasn't instinctive kindness, it was instinctive fear. (See Liz's incredibly weak "the younger generation just get this more than we do" line back at the office.)
By contrast, everyone's reactions to Piper's plight felt like they were coming from the heart. Piper was about to lose a spot she deserved to keep, through no fault of her own, because the system was set up to favour a transwoman over her. Not only that, but her entire sense of identity had been turned on its head in the most public and humiliating manner. The moment when the judge asked "does she know she'd be classified as that?" was particularly upsetting.
There was also a marked contrast between the ways Piper, Sadie and Melanie behaved in the courtroom. Sadie cried on the stand when the spotlight was on but was dry-eyed and angry when unobserved in the audience. Which leads me to think Sadie's predominant genuine emotion was anger at having this privilege questioned. Piper never got to speak at all, but sat crying silent tears in the audience. Predominant emotion: devastation. From Melanie's facial expressions and what little we see of her, I'd put her predominant emotions as hurt and confused. Three "girls". Three emotional responses. Spot the one odd one out.