> when an "insurer" fails to cover a loss of one of its insureds using its own providers or network, the insured can simply go to anyone they can find
A variation of this is in effect, though you have to know, and you have to push. If you as a consumer are given reason to believe by the insurer that the provider is in-network, then they are required to cover that provider as if they were in-network, even if not.
Specifically, if the carrier's "Provider Directory" lists that provider...
Challenges - this may not stop the initial out of network billing from the provider that you may have to pay and be reimbursed for, the tier 1 support representatives will stare blankly at you and have no idea what you're talking about, and when and if you get it escalated you'll have to fight for it.
(Also, admittedly, it's only really good for one 'encounter'. After that, the insurer will say that now you have a confirmed belief that they're out of network, so...)
The whole system is so broken.