I have seen that...
I saw some pics from museum with heavy crossbow with horn / sinew limbs ...
But for the physics sake :
For the composite bow - the lighter the limb - faster the bow will be. As wood core is lighter as horn - so bow should be faster.
Second - the core does close to nothing in the bending - and only skin of the bow does. Sinew layer for tension and horn layer for compresion forces.
Core is only for stability of the whole composite structure.
For example: Modern recurve competition bows use carbon limbs with rigid foam core (lighter than wood), rather than full carbon limb.
