Pappy Van Winkle, among others, made the distinction between "practical" distillers and "scientific" distillers. The distinction primarily has to do with yeast.
Practical distillers use, essentially, wild yeast. They create a medium of grains, water, hops, sulfur and other ingredients of personal preference, set it outside or--in the case of Jim Beam, out on the screened back porch of his house in Bardstown--and wait for nature to do its thing. Once a yeast has been captured in this way and begins to propagate, the yeast maker watches it, smells it and otherwise monitors it to determine if it will be good for making whiskey. If he thinks it will be, he continues to propagate it, then takes it to the distillery and tries it out.
Conversely, if he doesn't like the results, he pitches it and tries again.
A scientific distiller uses a pure strain yeast produced by a yeast company and propagates it in such a way as to avoid "infection" by wild yeast or other microorganisms.
The bridge between the two, of course, is that a yeast created originally by a practical distiller and proven to be good for whiskey making can be scientifically reproduced as a pure strain. I don't know which distilleries have done this but I am sure some of them have. Seagrams, for example, was proud of having created something like 5,000 different strains of yeast. These are called proprietary yeasts and are, I presume, patented or legally protected in some other way.
A wild yeast propagated in the traditional way is not equivalent to a pure strain because it mutates naturally and can express some variations. At some level this is acceptable but managing it is where the skills of the yeast maker come into play. The practical distiller takes steps of a traditional nature to prevent infection and excessive mutation. The most common and most effective of these, which is used by practical and scientific distillers alike, is the sour mash process.
A pure strain yeast is easier to manage and the skills are scientific in nature, whereas the practical distiller uses legerdemain and lore passed from father to son.