A and B do indeed look quite similar, both appear to weaken the idea that humans needed to use their hands freely to make advanced tools. However, there are two reasons why A does not directly apply to the argument.
Perhaps these animals do not stand upright, but for some other reason, they still have free use of their hands? Perhaps they sit on the ground, or anchor to a tree (like a sloth) with their legs, freeing up their hands. We do not know if these animals have very different anatomy from the early humans in question. More importantly, the tools in this answer choice are basic tools, while the tools in the argument are advanced tools. Perhaps it is easy to make basic tools with only limited hand use, but much harder to make advanced tools.