I think the key point is that the departure is a dynamic situation with an acceleration through Vmini, whereas the original requirements for Vmini revolve around longitudinal stability in trimmed flight. AC29 already makes provision for speeds below Vmini in the approach phase.
but you are flying with sole reference to instruments below Vmini - doesn't matter whether it is dynamic or not (in fact that is more hazardous than steady state with things like somatogravic illusions to contend with).
And this is a departure not an approach.