I just think there is more to it than "a provider exists." It has to have a supporting medical community.
Sure, I can agree with that. The availability of ACA compliant insurance plans doesn't mean they are necessarily the best choice for you, and you have always the opportunity to buy outside of the ACA exchanges. That didn't change when the ACA made their plans better.
Mostly, I think this 100% ACA availability report is news because it means the free market hasn't completely failed in these rural counties. Those places are difficult (barely profitable) markets for profit-driven insurance companies, but it turns out they are still profitable enough. Republicans in Congress have (strangely) argued that the free market failed to provide good comprehensive insurance to Americans in sparsely populated rural counties, and used this as evidence that the ACA was failing. The argument never really made sense to me anyway, but at least now they've lost the ability to make the argument.
The American health care system has some definite problems. Insurers pulling out out of the ACA exchanges isn't one of them.