I'm pretty sure he's talking about more darkness, not more light. But yes...more than 12 hours of light can stress it into hermie, or revert it back to a vegetative state.

Having said that...I've read many 'discussions' about this, but have no actual experience in doing it. I just don't know what benefits would be gained with more darkness. Decades ago, I was taught to veg at 18/6 and flower at 12/12. This is what I do, and it has worked just fine for many, many years.

Some of the more difficult strains, I have heard, need the light schedule modified a bit, but I haven't come across a strain I couldn't finish with 18/6 and 12/12.