[aerohead]

We got into this years ago, when 'Myth Busters' aired their episode with the clay-dimpled Ford Sedan.
1) I believe that the consensus was that, had they dimpled only the rearmost portion of the roof, and C-pillars, that that would have been enough to explain any observed drag reduction.
2) And the explanation had nothing to do with a transition from a laminar boundary-layer ( LBL ), to a turbulent boundary-layer ( TBL ),as is experienced with a dimpled golf ball, but rather that, as you mentioned, the dimples were actually functioning as vortex-generators submerged within a TBL, allowing re-attachment of separated flow onto the boot/ trunklid.
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If you want to 'get into the weeds' for an understanding of what happened, you might look around online for:
* critical roughness
* critical Reynolds number
* LBL to TBL transition point
* tangential force
* normal force
* momentum transfer
* displacement thickness
* pressure distribution
* viscous shearing
* momentum loss
* adverse pressure gradient
* termination of boundary-layer stability
* separation: reduced or negative pressure
* angle of flow @ separation point/line
* adhered & attached longitudinal vortices ( counter-rotating pair )
* turbulence
* Vortex generators ( artificial roughening / vortex-induced low pressure )
* 'Stationary' / 'locked' / 'captured' vortices
* reversal point
* reattachment
* mending
* pressure recovery
* jet-pump mechanism
* base drag
* pressure drag
* Boundary-layer theory by Prof. Dr.-Ing. Hermann Schlichting.