I find with more sativa dominant varieties 48 hours dark does push them into flower a little quicker than just going straight to 12/12, but more importantly they tend not to stretch so much in the first weeks of flower.
Just my experience tho and I have heard that this practice can stress your plants into becoming a little on the hermie side, never happened to me tho.
Try it you might like it
or if your cautious like me then give half your plants the shock treatment and half not, that way if the worse happens you can only go half wrong.