Surely someone from Boeing is available to give 'the horses mouth' answer. Centaurus claims the Boeing test boys have made this 'not recommended' decision, but yet they approve some operators to do it, or some just do it anyway.
It would be useful to understand, and therefore accept or not, the blanket statement of not recommended. It would also be educational; not a bad thing in this day and age. It would give a more in-depth knowledge of how the system works and what its short-comings are. Too often we barely scratch the surface with knowledge and just do as we are told. Then some rebel decides to experiment because it seems a possibility and good idea, and the system (which ever one) bites you in the backside: and then you discover why it was a 'do not'. Unbeknown to us button pushers on the outside there were some hidden gremlins lurking on the inside that a manufacture hadn't the time to fix and so did not want them woken up.
The days when an old friend of mine was a L-1011 captain in early 80's and pilots had a semi FE training are long gone. The FE had been replaced by buttons whose systems are interconnected via strange unknown routes. QRH's have replaced trouble-shooting manuals. Pilots play the piano at their peril. The memory of a tea & biscuits moment on a B767 when the A/T would not engage on takeoff. Captain climbed out and when well out of the TMA decided to reset the A/T cb. It still didn't work, but the RAT deployed and they returned. Oops!