Who came up with the NGK part number system?

I could probably accept using NGK and I do run a set in my 416. But, why in the hell do they have such a messed up part number? I years past dealing with Champion it was so simple. If you were using N12Y and you wanted resistor plug, simple add a R in front, RN12Y. Need a colder plug? Use a N-9Y. N denoted 3/4" reach plug Autolite was the same, running a 64 and you want a colder plug? Use 63. You have a BB use a J12Y or Autolite 85. J denoted a 3/8" reach plug. But as I just read in a slant 6 thread they were talking about a NGK zfr5n? What the hell kind of system is that? There doesn't seem to be a system here?