In Norway the IFC-format is approved as a national archive format for BIM-models.
This approval leads to requirement for a strict format versioning regime.
For a typical IFC-file the format version is given like this (from Archicad):
I don’t know if they are official buildingSMART ones, or specific to IfcOpenShell.
If buildingSMART does indeed have a list of official identifiers, then indeed, perhaps the vendors are just neglecting them or are unaware Would be interested to know the answer too!