That's why I always feel uncomfortable about being definite 'They never do this' or 'they will always do this'. Saying 'They usually...' is more the way I try and think.
You'll notice most serious biology stuff has disclaimers in it like "most, often, usually" next to virtually any otherwise "definitive" statement... LOL.
The not spiking from old bulbs is not actually always true. It surprised me as well! Yes it's true in the vast majority of cases, but not always.
I have a Colmanara Wildcat 'Botcat' which had two spikes from a bulb, then had several new growths eaten off (I think by a centipede). I was on the verge of throwing it out because I thought all the eyes would have gone when a new spike came up... from a 2 year old bulb which had already had two spikes! It came out from between two leaves closer to the bulb than the original two spikes.
I decided to keep it long enough to enjoy the flowers. When it was finishing blooming I noticed a new growth coming from eyes on one of the eaten off bits (and it was really only a couple of cm tall when eaten off so there was hardly anything for this new growth to grow out from. I still have it and it's just finished blooming again. But that's an aside... the point is that it DID bloom from an old growth, and really surprised me because it is accepted wisdom they don't do that. It's not done it again either