mark There are different factors that influence initial indexing speed, and disk performance is huge factor too. So, I cannot agree that the strategy you just laid out it optimal strategy for every case. I agree it could be optimal for PC without GPU but with very-very fast SSD, in other cases I would disagree.
Anyway, if you prefer yor archive to be indexed in two stages, you can just turn off face recognition initailly in “Library locations” and then turn it bank on later, this will give you desired effect.