Some of the hybrid albas do have some rebloom. Mme L. is believed my many experts to likely be an alba/noisette cross.
Vintage Garden reported that California growers of Alba semiplena and Alba maxima were seeing some fall rebloom.
Occasional rebloom on some albas is not altogether unheard of. OTOH, if you bought the everblooming Koningen von Denmark which was being sold in California nurseries in the late 90s, what you really got was a Portland, probably Jacques Cartier.
That would be a strong clue indeed. Could you point me in the direction of some books where this is discussed? The yellow in the petal bases of some Teas [via Chinas] has often been noted, but the Musk attributes knowledge is new to me. I'd like to learn more.