Don’t you think that opening the movie with some sort of Jedi training might give to ROJT a rehash feeling of TLJ ?
Well, one, we don’t know how TLJ will open, really. And two, no matter how you restructure the opening of ROTJ, there’s no training whatsoever to be seen - Luke has finished his training by the time the movie starts. In a restructure, it opens with Yoda telling Luke his training is complete and then dying. Don’t think TLJ will open like that, myself.