ListAdmin: Is list/archive working correctly?

For example, have been following the thread "Is there a better way? [combining f-string, thousands separator, right align]".
Me email (only) client shows a thread of 12 messages.
The OP was @Gilmeh Serda (from an invalid email address). That appears in the email thread
@Stefan Ram has had two contributions quoted, but no such original-message has appeared in the thread.
The archive is only showing seven contributions (for some reason Grant's recent contribution under the different subject line: "Formatting a str as a number" appears separately, even though it threads as the same conversation in email)
None of the OP's contributions appear!
IIRC the design has been that it doesn't matter if a contribution comes from the Newsgroup or the email Discussion List, they are treated the same. Are Newsgroup contributions being archived (were they ever)?
Is it user-error that some contributions don't appear on the list, but do appear in replies, or is there perhaps some other cause?
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Regards,
=dn