This is correct. The NCF really eats away at the value of these "free" inside cabins.
For reference, by waiting until the optimal time to book (48 days from sailing in this case), I got a second room for my August 2014 Alaska cruise for $109 over NCF/taxes. And I could have had it for $59 if I wanted a deck 4 cabin (I didn't). So someone with a certificate like yours saved a whopping $109 over what I paid on the open market.
The balcony staterooms which come with the 7 Stars program are a better deal.