I take your point about RTO-ing, and much might depend on day or night and weather conditions on departure, i.e. cloud base and vis for a return; also the length on the runway. RTO-ing does not necessarily mean max braking until a full-stop. So declaring it always an unnecessary RTO might be a little over simplifying a complicated scenario.
Because of all the aspects you mention giving this double failure on takeoff during a TR course is much too complicated at an early stage of training. During an RST as a pure confidence building and educational event is the correct stage, but because it will take a long time to complete with quality I doubt it features in many airlines programs. In my experience of various training syllabi the total AC failure (or double gen failure) is treated as so unlikely that it is often just a pure demo and discussion. Some allow a raw data ILS so two boxes can be ticked at the same time. What is missing is SBY instrument training. On NG it is a customer option, or was, to have PFD on SBY AC, thus a real small SBY ADI approach is not trained nor experienced. To me that is a gap that needs plugging. Some will argue it takes too many multiple failures to arrive in that situation, but it is a great confidence builder to fly such an approach. Great hand eye coordination and full understanding of Power/ATT control.