I hate to say it, but "person at the hydro store" should stick to hydroponics and not offer "advice" about things he does not understand. "Organic nutes" absolutely can burn plants, in more ways than one. Oftentimes in organics, less is more... You can't make a plant grow bigger or better by simply feeding it more.
Honestly, dude, you are in for a world of disappointment if you try to grow cannabis in a 3 gallon pot with 5 pounds of seabird guano in it.
Here are my predictions:
*Once you wet down that soil, the temperature will begin to rise. Greeted with a low carbon/nitrogen ratio and some moisture, bacteria and fungi present in the soil will very quickly multiply. In fact, they will feed and multiply so rapidly that they will noticably raise the temperature of the soil. They will also consume oxygen in the soil much faster than it can be replenished. Soon you will have a rapidly reproducing population of ANAEROBIC bacteria, complete with plenty of stinkiness and phytotoxic byproducts.
*If you plant seeds in it, they likely wont even germinate due to the toxic nitrogen levels.
*If you plant a clone in it, the clone will yellow, dry out, turn brown, and die. TOO MUCH NITROGEN!
YES, organic nutrients are less likely to burn plants, but they absolutely still can. Things like guano (bat or bird), blood meal, and alfalfa meal can burn plants. Other organic nutrients may be less likely to burn, but that doesn't mean you should add piles of them. It's all about having a BALANCE of the different nutrients, each at an appropriate concentration.