[Roy starts slightly at the disappearance, more because it's unexpected than because of any surprise at magic being used to make someone disappear. By the time Taako reappears, he's relaxed again.]

I think knowing that we can reach the Ethereal from here is valuable information in and of itself, honestly. [And kind of lucky for Taako.] Although it doesn't limit the assumptions we already have, unfortunately, it's at least evidence that we aren't wrong.