I have no idea, all I can tell you is it works as advertised on my AFD3/P45+ combo.
My guess is that the TTL flash sensor in the body has a translucent dome over it like an incident meter, and the reflectance of film emulsion and the digital sensor glass are not different enough to be a concern.
FWIW, the set ISO toggles over automatically, the auto head zoom to match mounted lens focal works too (however it only works in the 35mm mode, not the MF mode which is weird) and the wink fill works equally well when combined with the main (direct or bounced) in TTL too...
My guess is that the TTL flash sensor in the body has a translucent dome over it like an incident meter, and the reflectance of film emulsion and the digital sensor glass are not different enough to be a concern.
FWIW, the set ISO toggles over automatically, the auto head zoom to match mounted lens focal works too (however it only works in the 35mm mode, not the MF mode which is weird) and the wink fill works equally well when combined with the main (direct or bounced) in TTL too...