A cable backed bow can pick up an "effective recurve" at draw if the cord is stiffer than the tips. If you think of a limber stick with a cord running along one side you can see this - pull on the cord and the tip curls. Actually just look at how your fingers work.
The cable needs to be free to move though (within the strain limits of the materials - this won't be much) and the way forces are distributed, the pre-tensioning is important. The tension needs to be cranked in there for it to work, and If you think of the backing as a second bowstring, you can quickly see why leaving a hemp backed bow "string" for more than a few hours isn't on.
On the other hand, as me pointed out (I think you chose that alias just so it looks like we have atrocious grammar

) A backing can be useful while not adding draw. Even if it not adding strength, protecting the outer face from dents and scratches will prolong the life of the bow.
As for the idea of a glued-backing recurve bow, of course it is possible - that is what a modern laminated bow is after all, but that is a different beast. Hemp is stiff enough (maybe too stiff) that it would make a reasonable reinforcing fibre, but the construction would be very different.
Matthias