If you haven't been to First Rays Orchids, there is some information there concerning that particular fert.
I have seen differences in the cultivation habits of growers about nearly everything; my feeling is that each grower finds a balance in relation to his or her growing conditions. A difference in the concentration of fert could be due to the amount of light the plants are getting in each location, or the feeding schedule of the particular grower, or the genus of the plant itself.
just a simple example - my Stans are heavy feeders during growth, and can handle relatively high doses that my Phals cannot, even with all else being more or less equal. Also, I feed continuously at weaker concentrations, in some effort - perhaps misguided - to match the conditions they may experience out on the trees. (also, i admit, because the chances of me forgetting to feed, or when i last fed, are pretty good ) The change in light and temperature conditions as the season changed, and i feed less...hope i'm making some sense....
anyway, good growing, others will probably chime in too