Reducing hours of light progressively for starting flower doesnt speed up the process, its safer but it makes it slower. Swaping directly to 12/12 makes the plant produce chemicals that tell her its flower time so all that time youre reducing from 18 to 13 or 12, youre wasting it in my opinion. I have only had hermies once and it was because my timer broke and I didnt realize, they were getting 30 minutes of light during their dark period. I personally lean more to speed than safety because if theyre healthy and the genetic is stable they wont herm on you. As I said before I have a friend that works with quality clones and he gives them 1 entire day of darkness before 12/12 and his runs are very short, never hermies. I tried that this grow and out of 4 only 1 is a couple days behind, not a huge difference but noticeable. No stress, no hermies. Its easy to tell when theyre stressed, specially at the start of flower, when theyre stressed they wont grow as usual for a few days. Oh and he is one of the best growers in the region, his weed is always premium (partially due to the fact that he uses clones from the same mother than award winning plants from the spannabis, but also he is very experienced and has everything automated and in the perfect conditions).