I think the problem is line pilots thought Va for light a/c applied to large transport jets. The problem is the engineers or test pilots of transport a/c had different interpretations of what Va meant vs. what the line pilots thought it meant.
The problem here is...'thought it meant'.
Versus...what the actual certification criteria are in CAR4B/14CFR25.
If we look back more than thirty years with jet transport training, the trainers
then knew damn well what the problems were, and yet...the 'new breed' that came after, did
not, and further, would reject any input from older/more experienced guys.
The result?
A large number of dead bodies.
American Airlines (as a company) has a lot to answer for, with their misguided 'upset training' and will pay dearly, in the end.
Airboos, with their poor design, will also pay.
Meanwhile, dead bodies cannot speak from the grave....but their relatives can, through their attornies.
It will take at least 15 years to settle the legal action.