12/12 has never caused any issues for any plant, cannabis or otherwise. Problems are grower induced.
If growing for yield, there's a lot of things that are relevant more than more light.
Seems new growers always try the complex methods first, get poor results, then do it again thinking theres some trick they missed..
Breeders estimations are simply a sign post and should be used as basic info....add in your methods and it always changes.
AAMOF growing on 12/12 with environment within parameters, I've had some 10 week autos finish under 8 weeks seed to harvest.
Unusual but it does happen. Being my primary med, I'm picky about trics and always make sure they are mature to my choice, one for helping this and one for helping that.