If we go back to elementary chemistry, the only way your salt and sugar ratio would stay the same is to make a rub of these two things ONLY... in fact, he mentions this specifically. In bbq I KNOW he is not planning this.... When you ADD to any compound anything at all... the compound is not longer the same compound. He speaks of his RUB and sure the ration of the salt to sugar is such and such but in order to convey this relevantly we must consider the ENTIRE compound for it to mean anything.
I am glad you know what I am talking about... because I do. I know where you are going... you are considering simply the ration of salt to sugar, but in correct science, such as creating compound or a RUB you are speaking about the ratio of salt and sugar compared to whatever you put in there... otherwise, well, why don't you throw in 8 parts Cayenne and take a spoonful and tell me what time it is. Does it taste the same? LOL
When the man mentioned TASTE he has to consider overall whats in there. Thus, it no longer is a problem of the ratio of salt and sugar in isolation, but its ratio on the overall compound.