To some extent yes! You can call it a lot of things, but it is effectively digitally zooming ( cropping) into the Photo.
However, you loose pixels at the same time.
TC etc are not throwing away pixels. So, there is the difference.
Even when you "throw" away those pixel, you still got plenty left though. If memory serves correctly, doesn't it give you an 18mp file? Which is plenty. Hell my Nikon D90 is 12mp and i have not had any trouble with not having enough pixel to print. I've printed up to 20x24 without any issues. Just my 2 cents.