A MAC Address is too short to be an EUI-64 DevEUI. Earlier, there was an officially IEEE supported way to increase their length, but that has been deprecated as it clashed with official EUI-64 assignments. But still then: doing so is unlikely to cause conflicts within their usage in a specific network…
See also DevEUI for non-hardware assigned values. And just for the sake of completeness, but also unlikely to create problems: Generated Device EUI clashes with officially assigned EUIs.