Hence the requirement to remove them is the left seater isn't qualified on type, but I guess the bottom line is that if they are qualified on type and you do have them fitted the option is there for them to assist.
The practicalities of a non instructor/examiner taking over at short notice and without the cooperation of the right hand seat is a different matter. (The point I'm making badly here is that instructors probably have a good idea of the right level of effort involved and are probably seeing a situation develop from their experience on trial lessons. I was with somebody a while ago who froze on the pedals as we were lifting when I was in the left hand seat and all I could do was push the collective to the floor, so I do admire you guys and gals!)