Pset_CivilElementCommon, introduced in IFC4Add2 (4.0.2.0), mentions that the datatype of the Reference property is IfcLabel. However, all other Reference properties are generally IfcIdentifier. This issue persists in 4.0.2.1.
Possible mistake?
Hi,
correct - it is a mistake and will be fixed with the next documentation update 4.0.2.1 (and ongoing IFC4.2 work).
In addition there will be more work to ensure, that a property, like Reference, that is used in several property sets, is indeed only defined once (with one guid and one equivalence in the data dictionary). This however requires an update of the ifcDoc development tool.
Bump that this is still not resolved after over 2 years. I have referenced it here so it can be tracked for IFC 4.3 
Pset_CivilElementCommon.Reference should have a data type of IfcIdentifier not IfcLabel · Issue #17 · buildingSMART/IFC4.3.x-development · GitHub