I think what they say is *sometimes* true. There are many different kinds of intersex conditions.
Some *do* require medical treatment. Others do not. I know three different people that are intersexed and I'm close enough to know a bit of their medical history. One had life-threatening hormonal issues that required removal of gonads, another required surgery for fistulas and to ensure that their urethra functioned, and a third that has no external sex organs and is happy and healthy that way. There are plenty of intersexed people that never need any treatment (and in fact might not know they are intersexed).
Of the three, two are happily legally identified as "F", the other fights to be seen as intersexed - sometimes succeeding, sometimes failing, in the USA.
I've heard the thing about the Jewish tantum, but I don't know enough about Judiasm to know what basis in truth that has or how universally recognized it is.