Attributes in CA Spectrum's Attribute Editor and Attribute window are mapped with an attribute handle but if you check the same OID in MibTools the column is empty indicating that it is actually unmapped.
MibTools shows mappings that are done by the user and does not show mappings that are internal in Spectrum. There is no intelligence currently in Spectrum to know if a custom attribute mapping is being done on an already existing OID / external attribute.
This is documented in the CA Spectrum Certification User Guide:
Attribute Support Table
When you select a MIB in the Navigation panel, its attribute support details appear in the Attribute Support table. Find this table in the Map tab of the Contents panel. The Attribute Support table displays information for MIB objects and CA Spectrum attribute support.
Note: The table does not reflect the CA Spectrum attribute support from the CA Spectrum model type catalog. Only the CA Spectrum attribute support that is created using MIB Tools is included.