Calling HL7 a standards based interface is a very very large joke. It's about as 'standard' as semi-formatted XML document. Yeah you can communicate the structure, however each hospital/vendor/mapper implements where the data goes differently, hence the massive interop headaches.
While the NHL could generate their own canonical format for storage, they would still need to map it to each and every EMR they interacted with. Curious how they solved that one.