SFLY,
I'm both a Glider and a 777 Pilot and in this case, your Aerodynamics are simply wrong.
Best glide speed will give longest glide STEADY STATE. You CAN, however, extend glide beyond that by using energy by INCREASING AOA and flying at a reducing airspeed over a short priod. If the end of that period ic coincident with landing, you have optimised your performance.
Your contention is that the BA38 crew wolud have been better off maintaining a higher speed. simply-not-true.
If the aeroplane had been flown at best glide speed, it would have crashed short of the airport. Following the glideslope was the best idea available at the time, as it led to the runway! When that was no longer possible, dropping below G/S and landing short, but on the airfield led to what was, in the end, the optimum result available.
Let's make it clear- if they had done what you suggest most on board and probably may more on the ground would now be dead.
As to the Turkish crash, they had a servicable aircraft with two running engines that had a minor glitch. If we have seeded responsibility for monitoring airspeed to the automatics, we are entering a very dangerous phase in aviation history.
You are being given good gen by several competent people here, and largely ignoring it.
If you are a professional aviator, "I'm right and everyone else is wrong" is a dangerous attitude to hold.