Hmm. Never heard of that.Firstly, I'm likely the guy he's referring to since I'm the only former moderator who uses foliage pro all the way through flower.
however he also didn't mention that I also use potassium silicate to bump up the K and in flower my nutrient solution is about 70% foliage pro, 28% bloom and 2% potassium silicate. This brings the ratio closer to 2-1-2 and for late flower I aim for closer to 2-2-4 or 2-3-5 in that range. BUT, i have also used foliage pro and potassium silicate on their own for a full cycle with excellent results, and I know a lot of others who have too. But you need to add an additional source of K to balance it.
The numbers in NPK are percentages of the element in the bottle. Adding another element to "balance" it out it doesn't remove the first element. It just raises the nutrient load. You really don't need a ton of Pottasium anyway. It's not like Phosphorous, or Nitrogen, it's more of a regulating on/off switch, for things like the action of stomata, than N or P.
Potassium Silicate can be a nightmare especially when used with nutrient rich water. Crazy pH swings, major issues with other nutrients. It should be added to pure RO to prevent lock out... maybe that's why it works for you. You're locking out a ton of Nitro. I don't know. I will add that if you are using it at all for the benefit of Silica try a mono-silicic acid based instead. Much more affective
There is a balance between Potassium and Calcium, but I'd have to look it up. I only use Potassium beyond my base nutes in a PK booster and that's just a couple weeks.
If it works for you then great. It hasn't worked here at all.