The autoflowering trait is a recessive trait, the photoperiod trait is dominant.
when crossing an auto with a photoperiod you get mostly photoperiod depending if the photoperiods already carry the recessive trait or not
this actually how they breed for fast flowering strains:
What Are Fast Flowering Strains? Put simply, fast flowering cannabis is developed by mixing photoperiod and autoflowering strains. More precisely, by crossing the female clone of a feminized photoperiod strain with a feminized auto. This creates a strain that carries the autoflowering gene but is still light-dependent.
if the photoperiod already carry the auto gene then you ll get a mix of autos and photoperiods that's actually how they breed photo into auto after many successive cross