The workaround is now somewhat re-implementing Validator code.
There are some differences now between the parser because, in contrast to the legacy parser (that looks for the string "details" in the wikitext.) parsoid is actually looking for gendered subreferences.
Since this leads to more errors - for example when the references in unreachable - we might need to rephrase or create a separate error message.

The valid use case where a main ref is only defined in the reference list, but a subref is used in the article needs to be excluded.