In this SGA episode, it worked the same way. Their minds swapped bodies. So Keller's mind was in Casol's body and Casol's mind was in Keller's body. That's exactly what we saw in the episode. But keep in mind that the show will sometimes show us the body of the person talking, not the actual body to make it less confusing to the audience who is really talking. So when we see Keller's body on the planet, it was actually Keller's mind in Casol's body. We just see Keller to indicate who is really talking. The bodies did not switch, just the minds. Plus, it gives the main cast more screen time. Hopefully, I am not making it more confusing.