Personally, I try not to worry; good hobbyists have the method down. Those with experience, who aren't focused on selling you anything, will give you honest answers every time.
My experience with Seachem is that they'll list non-bioavailable nutrients on the analysis for their substrate. They'll also sell a fine dusting of chemicals in water, and call it trace elements, then charge you handsomely for it. By the time you turn to their dosing, you have instructions to under-dose your tank with dosage increases based on knee-jerks to deficiency. When turning to an old debate, you'll find snakeoil peddling tactics:
http://www.thekrib.com/Plants/Fertilizer/gluconate.html
In short, I don't like hunting down cases where, "Hey if they'll pay $6 for some fertilizer residue, and $25 for a small bag of crushed clay, why not give them what they want?" may be the actual, and unstated answer.
Now I'm not saying SeaChem products can't be useful under some circumstances where fertilizers are hard to get, or you have no desire to order 2L of glutaraldehyde as Cidex plus or similar. I've stopped wondering about their reasoning or instruction. Instead, I've started using their products (now rarely) on my own terms.