I would assume that the SOP's lederhosen is referring to explicitly allow FO's to use the LH tiller if that could save some time for emergency services to attend to an incapacitated captain (switching seats after landing. No one suggested landing from an unfamiliar seat). Regardless of SOPs, if the captain is incapacitated, it's an emergency and the FO as PIC may do whatever it takes. If there's a fast turn off, fine, use the pedals, if you stop on the runway and there are airstairs nearby, fine, but if it's an airport where using the tiller would help, for gods sake let the PIC make that decision. I think the FO on United Flight 1637 switched seats to use the tiller to get help for an incapacitated captain and I wouldn't ever second-guess someone who does. It's a decision that needs to be taken depending on circumstances, you can't create general rules for every emergency.