I have generally always started my seeds before spring equinox(12/12 light/dark) and either not used any supplemental lighting, or if I do use a light I mimic the natural light cycle. For me personally it's all about growth momentum and branching pattern, and preflowering can dramatically effect both.
One of the biggest motivating factors for me deciding to switch from growing clones to growing from seed was the preflower factor. I would plant a big beautiful bush of a clone in the ground(in May) next to a tiny, leggy seedling that I had started under natural lighting, the clone would sit there and do nothing for two to three weeks, the seedling would start growing from the start and never slow down, by the end of the year there would be no comparison.
Keeping a plants growth momentum plays a huge roll in how big a plant can get, I grow trees now, before I grew a few big ones every year, but usually about half would fail to meet my expectations.
Every time i try and plant before may 20, cold snaps, hail storms or wind storms get me replanting a few! Even low 60s in June a few years back had lotsa people digging up preflowering plants.
I'm confused by this statement, cold doesn't cause preflower. I live in the mountains where night temps are below 60 almost every night, have never had a plant started under natural light cycles preflower, ever, I've had them freeze and never preflower. I keep a grow journal and looking back I've planted the first week of May several times with no issue.
Perhaps I misunderstood your statement, not trying to be a dick, just trying to be helpful.
Good luck and happy growing everyone!