A broken light schedule like 12 hours on, 5 off, 1 on, then 6 off can confuse a plant.
The hour of light in the middle of what should be darkness stops it from going fully into flower. It throws off the plant’s natural rhythm (circadian) and makes it confused about what stage it’s in.
This kind of stress causes a spike in a growth hormone called gibberellin, which makes the plant stretch a lot. Since it’s not fully in veg or flower, it gets stuck in between and focuses on shooting upward.
You’ll often see way more vertical growth than usual. It’s the plant’s way of trying to adapt and reach for light, fast.
Can be great for filling an area, if your tactical with it.
I try it doesn’t promote as much vegetative growth as it does stretch. So it can reduce branching. It’s important to take timing into consideration, and overall goal.