Oh, you say that, but...
"Standards are anything but". I used to work for a company that wrote healthcare software, from EHRs to claims benefit management.
And our software was riddled with little transformers, because vendor A's implementation of HL7 behaved differently to vendor B's, and C's.
That's a different problem. The national networks have standardized APIs. Obviously the content returned will have some variations depending on the original source.