that guy is full of shit..... listen to the people that have used it not the salesman that guy is jerking you around trying to get you to buy more shit.
its all soluble nutes. maybe a little different composition or surfactant added, but not much else you can make your own nutes really cheap. its just easier to buy a bottle full. i wouldn't get to detailed on it because most all of its the same, little variations that are often irrelevant.
all any good nutrient is, some kind of surfactant most use a yucca extract, urea nitrogen, mono potassium phosphate, soluble potash, and mono ammonium phosphate. of course in the proper ratio with some water added and packaged or added and re-dried to make a nice powdered/flake mix.
dont let the hype get to ya man, yeah use that perlite up. lol i got to get some more myself.