@bear
If AB disabled SW< 60knots, would they have likewise programmed no WARNING at OVERSPEED? Seems logical?
In a spin, one can have forward A/S, and negative G/S. Fact is, it will always be 'negative' save for still air.
I would expect overspeed warning to only disable if IAS was invalid or somewhere beyond Mach 1.0 (no wings then anyway).
My point is that cross referencing ground speed at the onset of lost IAS they would see it reducing during the bizarre zoom climb. Either way if ground speed gradually from 400kts to close to zero it would indicate more an underspeed than an over speed. Giving a profoundly different perception.