I've gone back and read the SubOctavian post again and it sort of makes sense.
It's not "USN BBs are balanced". It's "USN BBs still crush CA". Ok, true. But they suffer against BBs, and there are more BBs than CA in the game.
In addition, the grand vision might be that your BBs will go after CA, and the CA will go after DDs and the DDs will go after BBs. In practice, that doesn't happen because that's not what the ships stats lend themselves too.
Reality looks more like:
BBs shoot at CA whenever they can because lolpen. When there are no CAs, BBs shoot at each other.
CA shoot at anything they can from behind islands or at long range because then they don't get deleted by BBs.
DDs fight other DDs for caps and then spot and sling random torpedos at whatever is out front.*
*BBs are rarely what's out front, and then only made in German BBs packing hydro.
So, BB vs BB is one of the main metrics a BB is measured by. All BBs do exceptionally well against CAs that they can fire back at. All BBs do exceptionally badly against anything they can't fire back at. Some BBs do exceptionally well vs other BBs, and some don't. So the main differentiation between the lines is not what range do they fight well at, it's can they handle a BB vs BB fight or not. At the mid to high tiers, IJN and KM BBs can handle other BBs, USN BBs really can't. That's all it comes down to.