Yes, that (and what you go on to say) all makes sense. However, it take me back to the question I asked flameport'. He asserted that "Cupboards are not enclosures" but, in terms of what we are saying, a cupboard accessed with a key would seem to be as 'secure' as many things which we would, without question, accept as an 'enclosure'.And I'd agree with him. Consider this, a typical CU only needs a common pattern screwdriver to open it - few people don't have access to a screwdriver that will fit well enough to open it, yet we don't consider that a problem.
Mind you, I can see a problem with that view. It could, for example be a whole room (or, I suppose if one wanted be silly, a whole house!) that could only be accessed with a key, but I don't think we would be happy for that room to be full of exposed single-insulated (not sheathed) conductors! ... so it's perhaps not totally straightforward.
Kind Regards, John