Ed has no idea Voltron is a person so he's just going to stay in his ignorant bubble and not harm himself mentally any further. At least, that's the plan.

He just nodded as Shiro explained about all of the weapons. The idea of giving Voltron a sword would be puzzling if he put thought into it, but he's just not. He's more focused on the reason Shiro began explaining all of this, anyway.

"So, because you don't have your bayard, you can't ... insert it in your lion and see the full potential." He's following. Mostly. "That means you also don't know what weapon it even is, right? If Keith's is a sword and everyone else's are personalized to them."