Yes, that's normal in insurance and NCD is for 1 vehicle. Even on the old Lynbrook insurance statement for 2 bikes it says 10yr for the BMW and N/A for the Norton. Aslo the NCD eveportes after 2 years not insuring.

I did nearly get bitten a while back as I had a bike NCD, but I insured 2 classics and the policy didn't apply the NCD. Fortunatly as I was renewing
for the 2nd time I noticed I was about to lose the NCD so moved to another insurer to keep it active.

Things were so much easier in the old days with an NU rider policy - no need to say what bike, just that it was under 350cc or under 600cc