I think it`s also used in Ilford Perceptol which is probably a Microdol clone. The old super-fine grain PPD developers had a reputation for poor speed yield and mushy definition, I believe that these were supplanted with DK-20 (Ilford ID-48 was similar) which contained Sodium Thiocyanate.
Originally Posted by Photo Engineer
This was also a silver solvent, but it too fell from favour due to causing dichroic fog and was superseded by Microdol and then Microdol-X.
With modern film technology, it seems unusual these days to use a developer that yields finer grain than those of the D-76 type as modern films already very fine grained.
Perhaps it`s more desirable to use a developer that keeps grain in check with films of ISO 125 and above that also exploits the full ISO film speed and to use a high definition developer with modern ISO 100 films and traditional slow emulsions.