I can confirm that the error happens when @Type is applied to a field/getter in a @MappedSuperclass. A possible (not a very nice) workaround might be to switch to property-based access, mark the property @Transient and override it in the child class.
I am surprised HIbernate does not provide a way to customize AttributeFactory or to use my own JpaMetamodelImplementor implementation. That would help to solve the issue without the need to wait for an official fix.