If I'm not mistaken it's not that they 'published' the finding as in 'publish in a peer-reviewed article' but more like depositing pre-print in a database (arXiv) for not yet peer-review journal.
it's simply not published in a peer-reviewed journal, but it is published on arXiv, as per definition of 'publishing', i.e. "the business of making books, magazines, or newspapers available to the public" (https://dictionary.cambridge.org/dictionary/english/publishi...)
True, but in academia and R&D, when researchers talk about "publications" they always refer to peer-reviewed journal publication unless stated otherwise.