Well, BSA did commercially remanufacture P-14s into sporting rifles, so there is such a rifle. But if yours is in unaltered military condition, I cannot see why it would have been so classified; except that as Stevo pointed out, the CFC is often not particularly accurate. Your mention of there being no markings on the receiver ring is puzzling. There should be markings there.
The CFC uses the terms "make" and "manufacturer" in their own special way.
This must be the case with my P14, I remember the verifier over the phone telling me it was sporterised(sp?), how she came to that conclusion I don't know but it makes sense of the situation now. Thanks!
P.S. The receiver is blank and clean that is correct