Well now. In a way, the shadow isn't surprised by this. After all, he knows what Akechi is truly like. Of course he would derail things. That's just in his nature.

"Does that make me your shadow as well? I am thou, thou art I."

Why yes, it's Shadow Ren's way of telling Akechi that he is Ren's shadow. Especially since Akechi likely heard those same words when he first awakened to his persona.

"I can certain do that. See how far I can go and give you that data you need."

Granted, there's no way he could go as far as Kamoshida. Not even Shadow Ren would be willing to go that far.