you need to strike business agreements with literally countless small practices, hospital systems, lab service providers, drug companies, outpatient clinics, etc.
This is why the aggregator model described in the article is relevant - the small practices will come to Amazon to plug into their aggregator and access their customers.
In that scenario, Amazon opens up shop in a state, provides cookie cutter TOS agreements to providers that mesh with the state's regulations, and providers on-board themselves in order to access the customer base.