I'm a personal injury attorney.
PIP/No-fault laws vary by state, but in my state, for example, a person who was injured in a car accident and suffered injuries would have his/her medical bills and records reviewed by a PIP/No-fault adjuster to determine if they are related, reasonable, etc. Obviously the insurance company needs to be able to review the actual records if they are being asked to pay the bills.
Most providers will include forms in your sign-up pack that gives them permission to send your bills/records directly to the insurance company, so the injured person doesn't have to get involved in that process.
That being said, PIP carriers can also be shady and try to get unrepresented people to sign blanket HIPAA releases and go "fishing" in prior meds, looking for a reason to deny payment. If I were counseling a friend or family member, and that person absolutely did NOT want to pursue a BI settlement, I'd want to them to at least sign only a LIMITED release specifying the provider (the provider who provided the accident-related treatment).