What specifically are they blocking? The most popular EHRs from vendors like Epic and Oracle have extensive interoperability APIs for multiple open industry sta

What specifically are they blocking? The most popular EHRs from vendors like Epic and Oracle have extensive interoperability APIs for multiple open industry standards. In general you can read all USCDI data pretty easily. Writing data is more limited, for understandable reasons. And if you want to distribute a SMART on FHIR app then you'll have to go through some sort of approval process. The strong vendor lock-in is unavoidable given how deeply an EHR gets embedded into any provider organization. No matter what regulators and standards bodies do, it will never be easy to switch.