my airline was the first NA carrier to fly the 320 and the 747-400, and, back in the day, the more we got of each, the more the airline's training dept (unofficially, as I remember it) encouraged the occasional use of manual thrust. (so as to maintain FLYING skills). But the airline didnt mandate either, unless required--obviously.
I cant imagine why manual thrust should be prohibited in line training? so, the first time I get to do it is, unsupervised?
how about, say, landing in sfo, lets try it there the first time.