I suppose it depends on how complicated you want to get into it, i think the simplest i can put it is,
In an F1 cross the dominant trait (or allele)within the 10 pairs of chromosomes relating to a plant make up will always show the dominant allele, which masks the recessive allele or trait. When you then start to create F2's (brother and sister plants making out) you find that both recessive and dominant traits will show through in the plant. Since the amount of documented testing on the plant that we have access to is fairly limited then as someone who is not a qualified scientist I would say that Photoperiod is one of those traits that are prevelant in a plant.
So it really depends on what generation of plant that is being discussed. There will always be a % of plants that are not effected by the photoperiod after you cross two of the F1 seeds (25% is a number thrown around) Further to that you are selecting plants for traits and subsequent breeding will provide dominant traits over recessive traits and the story goes on.
So if you have crossed an Ruderalis with a Normal indica in the initial F1's I would say that they would probably all be Photo light sensetive since this is a dominant trait in a ruderalis. However, what you also have to take into account is that your autoflower is a ruderalis that has been crossed with an indica or sativa (whatever, not sure what strain you have) So withouth knowing the exact genetic makeup of the seed stock that the breeder is selling, it would be difficult to be 100% accurate in a prognosis.
Hope that confuses you more, sorry. DST