It is entirely possible to inject (unrelated) wifi frames while being associated to a BSS without violating the existing 802.11 standards. That’s why Apple is able to implement AWDL on standard compliant wifi hardware.
However the path towards this type of interoperability would likely go through additional standardization via IEEE 802.11* and the Wi-Fi alliance. At which point Apple will need to implement and support the new standards. There is no need to reverse engineer AWDL to meet the new European interoperability requirements. What is needed is for wifi chipset OEMs to implement such standardization. Something pretty routine of them.
It can be expected that Apple will also maintain the proprietary AWDL in order to support their legacy devices.