Many such charts are confusing and end up chasing more things than you learn from them.
They also tend to be very general in terms of the expression of the symptoms. They all sound the same in other words. We deal with 300 species of plants, not one species. While references might suggest NH4 is preferred under specific circumstances and with specific species, that does not apply well to our system with 299 other plant species and generally, at least hopefully less, than 0.5ppm of NH4.
It's hardly a mandate.
The K+, Mg, Ca blocking baloney is just that.