incorrect reducing her feed in the final weeks of flower will deprive her of nutrients she needs at the most important time for her dropping back on the phos will cause her to cannibalize herself and turn purple. Also the lack of nitrogen at this stage will dramatically reduce your yield not to mention the lack of phosphorus which will hurt your yeild the most. Alot of growers tend to use the heaviest feed in the last 2 weeks for a reason and that reason is she will concentrate her hardest in them last weeks to bulk up as much as she can in order to make big flowers that will attract male pollen but for us it just means bigger fatter denser nugs :) What I will say is every different brand of nutrients also has its own feed table for a reason and if they say you get the best results from dropping the ec in the later weeks then fair enough im certainly not going to argue it or test it. I can only see a benefit to doing this maybe on the week before you intend to harvest but even then its still going to effect your yield. I mean this guy maybe right in his set up or the way he grows plants and he maybe trying to give you more flushing advice than growing advice. I visit grow shops on a regular and I find they are there to make money so they will try and sell you anything regardless weather you need it or not. They will probably advise dropping the nutrients and starting on a finishing agent flawless finish. which would require you to buy more lol though this is all just my opinion I have heard that green house seeds will flush thier plants before changing the nutrients schedule and they swear by it so maybe this is a variant on that where you are kind of flushing her ready to give her alot of flowering nutrients. that would be the only other thing i could see a use for it but personally I would stick to your feed table :)