In for a penny...I've never studied it but maybe point sources are unnatural and therefore more prone to disrupt the plant's cycle? I know @Smeegol grew big outside plants down the street from a streetlight.
Can't mention names. The guy from the horror movies.
Now I'm thinking of backing out of our bet. If it were true that lengthening light hours, but still short of 12, could overwhelm the flowering urge many growers in warm climates would, as you suggest, start their plants outdoors after December 21st. But we don't hear of anyone doing that under natural light.
Hmmm, who do I have to call to renegotiate the terms of the bet? I'd really prefer not to lose the house over this if it can be avoided. (Well, half a house 'cause I laid off part of it, but still.)