Read a bit more, posting status.
available from the Kindle Publishing Programs
describes in section 7 how to code inflections in dictionaries.
As I thought:
7.3 Inflections for Dictionaries
When building dictionaries, you may have multiple inflected forms of a single root word that should access the same entry. However, adding all of these inflected forms under the orthography (pronunciation) of a single entry leads to the generation of a large index, which negatively affects performance and user experience. Kindle has a disinflection engine that uses a set of rules for disinflecting any given word to its headword. The index then has only the headword to look up.
To generate the set of disinflection rules for the dictionary, the input must include some information about the inflections. There are two ways to provide this information: simplified inflection syntax and advanced inflection syntax.
7.3.1 Advanced inflection syntax
Inflections are handled by the inflection index, which is built into the dictionary based on the inflected forms which are tagged in the content using the <idx:infl> tag. Inflections are attached to the orthography of the entry. They must be specified inside of an <idx: orth> tag. If an entry has multiple orthographies, each must have its own inflections.
<idx:iform name="plural" value="records" />
<idx:iform name="present participle" value="recording" />
<idx:iform name="past participle" value="recorded" />
<idx:iform name="present 3ps" value="records" />
The inflgrp and name attributes are optional. The idx:infl, idx:iform, and value attributes are mandatory.
7.3.2 Simplified inflection syntax
For English dictionaries, simplified inflection syntax is a very simple way of giving information about the inflections. Previous versions of the file format supported using the infl attribute in either the <idx: orth> or the <idx:gramgrp> tag and specifying a comma-separated list of inflected forms. This syntax is now deprecated, as it is not as accurate when disinflecting, particularly for non-English languages.
So it must be that the Smirnitsky dictionary has these defined. I am attempting to decompile so I can verify by inspecting the source .opf
So far, Calibre conversion .mobi to .htmlz shows single entries
and Calibre conversion .mobi to .epub never completes
To be continued...