One of the biggest barriers to learning about sake is the terminology used to define the various grades. It is not a simple linguistic matter, as even the average Japanese person, more often than not, does not know specifically to what the terminology refers. These terms were not coined at once, nor do they reflect a carefully planned grading scheme, as was the case for wine. Rather, they emerged haphazardly and piecemeal in response to market changes.
For example, until World War II, all sake was made with only rice and no additives. There was no need to call it junmaishu, today's term for such sake, as at the time there was nothing else. It was only when the adulteration of sake with liberal amounts of distilled alcohol became increasingly common that the need arose for a "rice-only sake" descriptive term.
Same with the term honjozo, which indicates a sake made by the "original brewing method." In the strictest sense this tag is inaccurate, as a small amount of distilled alcohol is added. But the term emerged in response to market changes, as a way to tell the public, "We are not adding tons of pure alcohol, sugar and acids to increase yields, just a tad of alcohol, and only to smoothen the flavor."