Yes, you had mentioned that earlier and it makes sense. I repeat what I quoted from Gabe elsewhere just now, "this only happens if there are Waffen-SS units present in the imported core (or maybe owning the spec is enough). Does not happen with a DAK core if you buy the Waffen-SS spec later, for example."
These Waffen SS units already have certain specs attached to them and if they now share Wehrmacht specs when imported, the Wehrmacht effects that award extra CPs and RPs, like the Waffen SS specialisation itself and War Economy and Female Factory Labor, are doubled for that reason.
I now understand this issue, thanks to you and Gabe.