Hi Volume
Some years ago I was flying the older Dash-8s , which had a slow/fast indicator on the left side of the ADI.
This in fact was a kind of an angle of attack indicator, and you could use it using it during the approach.
The "on-speed" indication was a 1.3 of the VS (stall speed at a given configuration).
Since the calculated Vref is based on the stall speed in landing configuration, the AOA indication is usefull.
I believe many fighter pilots entirely rely on AOA (not speed) during approach and landing.
Brgds
SE210