Insurance denial and self pay not allowed for child’s surgery

Posting for a friend. Long story short, my friend’s kiddo has suffered with epilepsy for about 2 years. He’s on day 7 of a hospital stay at a Seton Ascension children’s hospital where they implanted leads into the brain to figure out where the seizures were coming from and then they were to perform a corrective surgery when removing the leads – either a craniotomy or an ablation. Surgery slot is set for tomorrow. Good news! The neuro team feels confident the ablation is the best route to go. But United has been denying prior auth only for the ablation for weeks. They have no issue paying for a full craniotomy. Hospital says United is the only carrier who doesn’t cover this type of procedure and they’ve been in a battle with United Healthcare over coverage/payment terms for years. My friend offered to pay out of pocket and was told that also was not an option (not sure why). His leads will be removed tomorrow. But they will be sent home without any corrective surgery to “fight it out” with the insurance company. Can someone explain to me why they wouldn’t be able to pay out of pocket? Can a complaint against United be filed? Everyone seems more interested in figuring out money vs taking care of a 7 year old kid.

Edit to Add: this is an employer sponsored United HealthCare Plan.