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If you start them on 13ish and the sun gets to 14.5 outside some plants will stay in veg, some will flower. It's really strain dependent as well. I think sativas are more likely to flower with shorter light times as most of the places they grow naturally have very long days. If you pick an indica with lineag sourced somewhere where summers are around 14-15 hours max you probably have a much better chance. You risk the getting confused and swapping back and fourth from veg to flower as well though.14 : 30 is the most light my area ever gets ; i will test it regardless if nobody knows for sure
Sativas are generally from equatorial areas. These areas are not known for long days just the opposite. They stay consistently around 12/14 hours of daylight. The northern and southern hemisphere get the longer days in there respective summers. Kinda like Alaska and 20 hours of light in summer and the opposite in winter. It goes with the rotation of the earth around the sun.
I'm in Los Angeles. And the reason that the outdoor works here is because we plant when the days are around 13 in May and the days get longer for a months and a half. I've never seen a plant flower under the circumstance that light period is getting longer every day. The days also gradually get shorter, which is why they take longer to flower and why you have that 4-6 weeks before they start to flower. It's not that it doesn't notice the days getting shorter, outdoor is just a much more gradual transition in all cases than most indoor setups.
That's an interesting thought. Ime as long as you plant when the days are getting longer, you're good. But if you plant at longest day length there about a 50/50 chance your plant goes into flower or some confused state between veg and flower if your days are 14 hours or less.