I imagine- if a 'patient' wants to back out of the procedure- due to SI or, anything else- they would be able to. I imagine that's why many methods used rely on the person themself administering the method. With nembutal- the person will ultimately decide whether or not to drink it. With the Sarco pod- I'm guessing it's computerised and they get to confirm or reject the final decision inside the pod.
I doubt the person with them would try to convince them either way at that stage. They are just presenting them with the option they requested.
But yes, I agree. I imagine it's got to be a very emotional thing to witness and potentially distressing- if they become distressed. Can't be an easy thing to do. They must be 100% convinced that it's right that people should get the choice. I do really admire them. Even though I believe in the right to die, I think I'd still cry witnessing it.