V for Velocity.
100%.
No argument.
VS is indeed a vertical speed mode in Flight Guidance Systems / autopilots. Nothing to do with V1/Vr/V2/Vmca etc.
I also agree that Vat is used to define aircraft Category (A,B or C etc.) for approach purposes. Vref changes with weight on the day but Vat, for PANS OPS purposes, remains a fixed max weight speed.