I have no idea if the turbulance mode can or can't be used in RVSM airspace. If however I asked a FO to do something I would expect that he would do that. If he said bullship and did it anyway he would be replaced on the next leg. I had lots of Captains with strange concepts. As long as it was not unsafe I did it they way they want. When you get to be Captain you can do it the way you want. If you feel its a big deviation from SOP then you can go to professional standards or as a last resort the CP after the trip.