isn't the 650ti boost a crippled 660?
This is 100% true.
Most mid level gpu's are just cut down versions of higher end ones.
They can take a 660 that did not have enough working shaders and make a 650 ti boost.
They can take a 650 ti boost that does is not good enough to boost and only has part of its memory controller working and make a 650 ti.
This is not uncommon. AMD's tri core cpus had all been quad cores with cores that did not work. At a point they had such demand that fully functional quad core cpus would have a core disabled just to get enough made. This lead to people unlocking cores on those cpus. The same has been done with some video cards in the past.