Fwiw, if one has a passport and some funds, one can travel abroad for cheaper surgery abroad. It won't guarantee an outcome, but it ought to be better than delaying it. Of course this in no way excuses the insurance firm.
Any of them.
They all behave in this exact same fucking way. Every single one has horror stories like this.
Sometimes you get lucky, and they don't fuck your particular case over, sometimes you don't.
So far over $5M into complex cancer care at the fanciest clinics in the world and never been questioned on a single claim.