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.
Reference the "Attribute Support Table" section of the documentation for more information.