@LemonadeJoe don't mean to be picky but since it's light cycles we are discussing, should probably correct the typo on "12/2". Nobody's going to be flowering on that cycle. But I agree with your conclusions.
Light cycle manipulation can work to meet specific goals, but there are always compromises. Mainly, shortening hours of light below about 18 per 24-cycle, or using a shorter day cycle in bloom, may "scramble the energy signature" or finish crops faster, but at the cost of growth rate and flower production. So it becomes a trade-off between finishing a room say, 15% quicker, but losing 20% of finished weight. Each combination of strain and lighting regime will yield different results, but I've yet to see significant, reproducible results from light cycles that strayed much beyond the standard formats.
It doesn't have to be a guessing game as to how much light is optimum for growing cannabis. The greenhouse industry uses a species-specific metric called Daily Light Integral (DLI) to measure the intensity over time of light needed to bring a healthy crop to optimum harvest. Here's a good primer on DLI:
The specific optimum DLI for cannabis has not been rigorously established, but it is assumed to be similar to other C3 species such as tomatoes and peppers.
There was a very good discussion of DLI and PFFD requirements of cannabis in an ICMag thread a few years ago by researcher focused on this area. The quote below is his conclusion on DLI requirements:
In our experience between 30 and 55 DLI (mol/m-2/day-1 in the PAR range) is good for Cannabis in all growth stages. Like PPFD, only use higher DLI in well controlled environments, such as temperature, VPD and CO2.
Here's a quick way to convert PPFD to DLI; this is only valid for indoor or supplemental lighting greenhouses:
(PPFD)(hours of light per day)(0.0036) = DLI
Now, 55 DLI is equal to Northern California latitude mid-day sun in July. Difficult to achieve in most indoor spaces. A 2016 High Times article puts optimum indoor DLI at 25-30, and suggests any more intensity requires CO2 to use effectively.