i generally run my lights 12 hours on and 12 off. i've never had a problem with this, and i always have more than enough light, so intensity has never been a problem for me either.
i maintain a tank at a gym and i am the only one that feeds the tank. i visit it 2 times a week to do so, and the fish are fat and happy. when i do a water change, the water that comes out is still yellow, even with 2x a week feedings, and weekly changes.
everything you put in the tank must come out. even when it's eaten, it's still there, it's just changed a bit.
I've only used a UV sterilizer one time in my life and that was because i had a "green water" outbreak on that gym tank. The sterilizer kills whatever passes through it, so it worked to correct it. i haven't used it since.
The science, is just that- if you can get the cyano to pass through the sterilizer, instead of just spreading around on surfaces, it may be effective, but the only way it will work is if you use ultraviolet light on the entire tank, which would be detrimental to more than just the algae.