Is NEC code for non-metallic cable applicable now that I've installed an attic ladder?
I would say no.

The rule is likely for attics that can be readily accessed. For instance, some houses have an access door (think closet door) in the top level of the house that leads into the attic. If someone can just open a door and go in, it's accessible (but it's probably also decked, lest someone open it and fall downstairs).

I bought a brand new house not long ago and there was an attic access panel in the ceiling of the garage (the HVAC unit was up there so it would be silly to have it sealed). None of the wires in the attic were protected because it was still difficult to get up there. Even after adding attic stairs, it wasn't something that you could "just go into". I doubt they could have passed inspections if code had meant "cannot be accessed by anyone", which would probably be a code violation in most areas.