Hazelnuts et al-
MINIMUM V2 is based on Vs, but that isn't always the one that is used.
It seems that the point is that Stopstarts operation uses a fairly simple definition of V2.
As Jammedstab pointed out, it CAN be different, particularly if using a performance optimising tool.
In that case, V2 can't be less than Vr, and both can be considerably more than Vref 30 in order to utilise excess runway to improve RTOW.