Create valid PDF/A part 2 or 3 with font subset

When creating PDF/A-2a or PDF/A-3a with font embedding mode "subset" the resulting PDF in not valid according to veraPDF which reports:
Specification: ISO 19005-3:2012, Clause: 6.2.11.4, Test number: 4. If the FontDescriptor dictionary of an embedded CID font contains a CIDSet stream, then it shall identify all CIDs which are present in the font program, regardless of whether a CID in the font is referenced or used by the PDF or not.

Embedding the complete font seems to solve the validation error but resulting files are very large.

When exporting files as PDF/A from Microsoft Word the PDF is valid and it only contains a subset of the font.

The only difference I noticed is that Word does not create a CIDSet.

File samples.zip contains two PDF/A-3a created by Word and the files used to create the same PDFs with FOP.