As far as I am concerned, ADR 5 can level a building. I'm not so sure about the tactical nuke part: I'm not the one that made up the comparisons and frankly that's not how I'd GM it.
I mean, people say that most anti-starship weapons could fire down on a planet and obliterate a continent. but, when fired on a starship (something arguably smaller), the ship - even shieldless - seems to be able to take the hit. In light of that, is the weapon truly capable of destroying a planet when it doesn't destroy a ship?
If you want to point your finger at inconsistencies, they are there. No amount of rule lawyering is going to remove them, whatever the damage scale taken unless you go for a very draconian one.
You could, of course. I'm just not sure many plotships will stick to it. As a GM, I sure wouldn't - I prefer my ship being able to take hits, use that as a factor for increased tension and something to promote roleplay.