So the ailerons still have effect (mostly for beginning pilots).
Debatable (the part about for beginning pilots). Actually, the whole argument about stalls beginning at the trailing edge is immaterial to the pilot, what is important to the pilot is maintaining control, adequate stall warning so he can maximize performance without inordinate fear of stall/departure, and an easily recoverable stall. A wing is a three-dimensional surface and designers do design aircraft (even now) so that an inner wing surface will stall before the tip does. That is one of the points to washout (whether generated by twist or differences in the airfoil section) and stall strips (which are specifically designed to trigger localized stall on an inboard section of a wing. It is not something done only for beginning pilots and trainers although trainers are likely to have a more pronounced washout and stall warning. Even now with advanced fly-by-wire control systems and automatic maneuvering flaps/slats in modern fighters washout is still used.
The idea that in a "perfect world" the entire wing would stall at the same time is theoretically correct as the wing's maximum potential lift would be generated because the entire wing is at it's CLmax just prior to stall, however, once you go past critical AoA the entire wing will stall, sometimes abruptly. This is not a good thing in the real world. First, stalling at the wingtips destroys aileron effectiveness and therefore control. Second, there would be little margin for error when operating near critical AoA, and third, the stall would tend to be abrupt. The designers chore is to arrive at a good balance of warning, control and performance. Pilots need to be able to ride the edge of stall for maximum turn performance while maintaining control (while doing some fairly abrupt control movements) and designing a wing so that the inboard sections begin to stall first enhances his ability to do this.
The P51 stall video is nice but is only one condition; a wings level, unaccelerated stall and therefore mostly irrelevant to the discussion of ACM where accelerated stalls are the problem. The film is of a benign slow speed, wings level stall while the problems of abrupt and violent stall/departure occurs during accelerated stalls. You have to carefully note under what circumstances a test or discussion is related to before jumping to conclusions. Many aircraft can have a benign approach configuration stall yet still have an abrupt and violent accelerated stall.
Also, the argument that buffet on the P51's tail is caused by "induced drag" is incorrect. It is related only in that induced drag increases with increasing lift but the source of induced drag isn't separated airflow but wingtip vortices's and the inclination of the lift vector relative to the flightpath. A burble is created when the airflow begins to separate from the wing surface, i.e., at the beginning of a stall which is convenient since separation of airflow is the definition of stall. The fact that induced drag occurs at the same time is irrelevant. It is the burble from the stalled section of wing impacting the tail surfaces which causes the stick to tremble.
