There's a reason people prefer weapons; they take a lot less training to be effectively deadly with than the human body. However, when it comes to coordination, the human body has a rather large advantage in that the human brain is evolved to control it. Added bits of wood and metal add on considerations for which the human brain is not structured. It requires adaptation to a different balance, the need to maintain a controlling (but not excessive) grip, the fact that you now have "appendages" with no neural feedback to either kinesthetic awareness or the sense of touch, and probably other factors I am not thinking of. I don't think there is a clear and definite real-world answer to your question, because you've got this issues that can allow arguing either way. So you need to think about game balance only, then slap on a rationalization if you need one.
Note that regular martial arts attack in Rolemaster do one attack roll in spite of using the entire body. It does not have the same advantage in game terms as TWC. Be wary of giving away too much. Maybe let an NPC have that advantage and if it seems overly tough when fighting the PCs, you'll know to disallow easy Martial Arts TWC in the future. OTOH, if someone wants to use two-handed stick-fighting and accepts treating it the same as any club, why not? Maybe even say it is equivalent to a staff if you are generous, but not a double attack roll.