Haworthia subretusa (Dr. M Hayashi) grows naturally in the vicinity of Heidelberg in the Western Cape. In this area Haworthia retusa grades into various forms of Haworthia turgida and the usually small retuse Haworthia heidelbergensis.
Although Haworthia subretusa is very similar to Haworthia retusa it is a proliferous plant as compared to the latter which is more often solitary or slowly proliferous. This comparison of course excludes the proliferous Haworthia geraldii and Haworthia fouchei plants from Riversdale.
Due to the variation of retuse Haworthias in the Heidelberg area it is difficult to apply the name with exactness to multiple forms. It does make sense to uphold the name I think as it provides another 'anchor' from which to compare other Haworthias in the area.