It may be that the FEO is treating this FAC holder [with proven AOLQ history in another U.K. county] as an " unknown" entity by invoking this section:

Guide on firearms licensing law (accessible)
If so, I feel sure this can be robustly challenged by showing (1) length of FAC ownership (2) evidence of previous U.K. stalks - unguided would be useful, previous permissioning letters from contactable land owners, cull records, etc (3) receipts from overseas uses of rifle including .375