Regardless he's showing a deficiency. Dosing extra K will only help so it's a no-brainer to put it in. K get's used up very quickly in co2/good light. Personally I would do that than go by the notion that there is 'suppose' to be enough from the other two macros.
Your approach is definitely understandable. For some time I also thought I was also missing potassium and started to dose K2SO4 to make up for my deficency.
But with the EI dosing I worked out by molecular mass that it would be a ratio of 1: .08 : .15 of NPK. Which should be sufficient. The numbers might be off a little. I have to find my notes but my point is that the potassium is not at at a level that's below the minimum threshold.
Also I never noticed any difference when adding or not adding K2SO4 as long as I use the EI routine