At the time of the F3 introduction, the local Nikon importer said the feature was specifically implemented for the sake of professionals who might load a film with the lens cap on - which in turn would result in a multi second long exposure delaying the film loading process and thereby causing lost precious time.
Before the introduction of the F3, the Nikon FE was widely used by pros as a secondary camera to the F2 - and the feedback given to Nikon was that the blockage of film advance during film loading was a problem, hence the birth of this feature - the customers asked for it
It would be kind of ironic if the F3P didn't also have this feature.
Thank you very much for that information. Very interesting.