Are products without types allowed?

I might’ve missed something, but in the spec I could not see anywhere which forbid a product that isn’t typed by a type product. I think this is a good thing, as very often there are objects where the type isn’t known or doesn’t make sense (e.g. a one-off product, or a scan of an unidentified item). Can others here confirm that an untyped product is legal behaviour?

The reason I ask is because in Revit, for example, everything is typed by default and I am unsure how to tell it not to type a product.

Yes. Typing in the RV1.2 is optional. The schema itself also has the inverse attribute IfcObject.IsTypedBy marked as optional.

IfcBuildingElement entities then have this where rule:
CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR ('IFCSHAREDBLDGELEMENTS.IfcBeamType' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));

Saying that either you do not have a Type or it has to be in this IfcBeam example the correct one which is from the from the IfcSharedBldgElements data schema IfcBeamType.