Once the seed pops, the clock is ticking. You see, autoflowers are from a mix of photoperiod cannabis and cannabis ruderalis. Cannabis ruderalis is native to Siberia. Since Siberia doesn't have a long growing season, a process of natural selection occurred when cannabis found its way there; indicas that flowered earlier survived better compared to sativas. Because of the harsh growing environment, bud size and thc content on the ruderalis dimished to the point that it no longer resembled it's indica cousins. Because of these adaptations the ruderalis developed an internal clock in its genetic structure- once the root comes out it has about 2-3 weeks of veg growth before it starts the flower cycle because the plant thinks it only has 7 weeks to insure the next generation. When indicas or sativas get crossed with ruderalis, the flavor, potency, and (relative) bud size of the indica/sativa get mixed with the internal clock of the ruderalis strain. The only reason ruderalis has this tendency is because of where it evolved, and it is that tendency that will keep cloning from being an effective means of continuing the strain. The only way to successfully do this with autoflowers is pollination, and then you start to get into genetics. Depending on how the strain you buy was developed this could be easy (if it is the 3rd generation of the strain) or difficult/long (if you are getting 1st gen seeds from a ruderalis-indica or sativa hybrid.
