I don't think he's saying that your medium and light armor choices would have to be equable or only slightly inferior to heavy/Power Armor.
What he is saying is that you should be able to choose a light armor or medium armor and not be totally screwed when going for end game battles.
Deciding to use the light or medium armor variants would off course offer less protection, which would ideally be off set by some other bonus (either through perks or intrinsic).
I was actually accounting for all of that in my assessment, but I'll expand on it a bit to clarify.
Traditionally, end-game opposition is supposed to be of a threat level that provides a goodly amount of risk for a character in the best gear. As such, wearing anything less is usually guaranteed death, which is why RPGs offer better and better equipment as the game and/or the character's level progress. Wearing Medium, let alone Light, armors against end-game content isn't
meant to be even remotely viable in the end-game, as doing so would break the entire armor system, so no provision is made to allow it.
In order to go against this, you have to do one of two things: either nerf the crap out of the opposition, or buff the hell out of the light(er) armors in order to make them competitive with the heavy stuff. This will have the effect of putting the efficacy of the lighter classes too close to that of Heavy, which is exactly what you're trying to avoid.
Deciding to wear the lighter types for less protection should mean exactly that:
less protection. Unfortunately, it doesn't, because the sorts of weapons you'd want to wear the Heavy stuff against blow right through it anyway thanks to the absence of DR. If anything, you're
better-protected in Light Armor, because you can nullify the opposition's ability to get critical hits while simultaneously running rings around them and strafing them to death, whereas Medium and Heavy Armors cannot offer anything like that and have only their DT to lean on, which doesn't go that far once you start facing high-end opposition.