They shouldn't be classed or marketed as autos if you have to change the light cycle. If people are growing different strains it could cause problems. You'd either not realise you needed to change cycle to induce flowering on certain strains and end up confused with stressed plants or have to switch to change cycle reducing the yield on the "true" autos. The idea of autos is they flower under any light cycle, which allows growers to run plants at different stages continuously, that's one of the major advantage's.