well i put my plants out in april and there flowering the days are shorter than 14 hours which means some plants will flower there are not too many days over 14 hours. if your growing from clones that were under 18/6 or 24 hour light cycles it matters they will flower on days longer than 12 hours there are 5 months of more than 12 light hour days but not very many days over 14 which some plants need depending on how they were vegged. plants grown from seed outdoors adjust differently to light cycles. i just put out a fresh clone we will see if it also flowers also hopefully not.
I believe the hour marker your talking about is more like 13 hours of light, or slightly more. Rhuderalis strains will flower anytime all the time. I have been putting seedlings and clones out (some started inside, some done completely outside) for years... only twice did plants START to flower in early to mid April, then going right back into veg.... basically just showing sex (or in the case of the clones, starting calyx development in clusters) and going back into veg...
It may have to do with placement as well. I put clones that were recieving both 24 hrs of light, and 18 hours of light, outside and they started getting 13.3 hrs of light (measured myself) no flowering on them even though this year I did it and they are fully mature and preflowering like crazy. Figures....
If a clone was taken from the mother while the mother was flowering, and you put it outside than thats a different story....