It seems elegantly simple.
Just depends on which way you apply parallax to your contemplation.
If the machine knows the incidence (plus the other stuff), it knows the (approximate) weight which gives the Vs and V/Vs. So there is no problem representing things by a simple relationship between incidence and V/Vs. If that explanation floats your boat comfortably then run with it.
One needs to be a little careful extolling the virtues of incidence measurements - useful at high alpha but still subject to errors like everything else we deal with and a fairly coarse measurement - which is one of the reasons why the certification fraternity tends to stick with the weights and speeds side of things.
Just how the OEMs implement this stuff in the black boxes I can't say, but the underlying basics philosophically are fairly straightforward.