I still haven’t heard from Florian but I do have it on good authority that the spoke heads need to sit on the flat side, with the J-bend being on the countersunk side.
This page also back up this point to a T:
If I’d have built these wheels myself I’d have gone the other way, based on the visuals of the countersinking matching the heads of spokes. Hopefully this helps people avoid a rookie mistake with lacing etc 
(Still curious what Florian says, but I now highly doubt he’ll go against this clearly understood wheel building principle)