The Ore Dict system was designed so that multiple mods that added "copper" could all use each other's ingots in their recipes (because why would IC2's copper not work in Thaumcraft?). But this got extended to wood, so that oak, birth, spruce, pine, redwood, willow, ceder, fir, etc. into "wood" for recipes that just wanted "wood."
And it mutated from there. Different kinds of "sticks" or "seeds" or "wheat" or "corn" or any other thing you could ever want that someone else might've already made and you want to insure compatibility.