"If you're using less light, you'll need less CO2 to be effective, though you won't be getting as much an increase in growth compared to if you were using stronger lights."
The only reference to waste, at least in the article I read. Was reverencing to ineffective setups and flooding co2 in the dark cycle.
So for me, to toss in a jug of yeast an sugar water, which costs nothing virtually because I already have it. Its like, "Why not? Cant hurt" Now, Would I go add a fancy co2 regulator and tank. No. Not with low level lights. But I have been using co2 on plants for years. Loooooong before I ever even smoked weed. I used it for aquatic plants, so its just kinda became part of my plant regiment. Ive seen what it can do for plants so for me its just like that one extra bit. But id hardly call it waste.