Eu vi um dos respostas isso diz;
This was actually a huge shock for Palpatine, for even though he'd been told by Dooku that Yoda was actually able to repulse force lighting, something that no light side user was ever known to do, Sidious still didn’t expect Yoda to be able to deflect someone at his level. That is why Palpatine had a shocked look on his face when Yoda began to push back against the lightning.
Então isso basicamente responde à pergunta. Mas aqui está a minha pergunta agora, Existe / há alguma evidência de que Dookan / Tyranus tenha contado isso a seu mestre Sidious? Tais como as novelizações, lendas e quadrinhos. Em outras palavras, estou apenas perguntando se Tyranus dizendo a Sidious que ele lutou com Yoda se justifica nas evidências sugeridas. =)