I would bet Boeing doesn't recommend its use has more to do with a lack of training and proficiency than its usefulness.
Like I said before, if I hadn't got used to it on a HUD, I don't know if I would have ever gotten used to it.
I can't think of any FPV that has ANY pitot static input. It should be coming straight from the INS.
Boeing and Airbus training for unreliable speed makes one HUGE assumption of power and pitch: That is that you are close to the desired speed. If you bled off a bunch of speed, or are too fast, you have to get back to the correct speed before pitch and power do any good.
I prefer just flying AOA, which I can do because, well, I used to do it in a HUD. They should train it more.