Why does Kopernio find "OA Alternative" when the OA is from the publisher?

Looking at an OA article on a publisher's site, Kopernio pops up and says it found an "OA alternative." When I click through to the PDF in Kopernio and check the link where it got the article, it was from the publisher. So shouldn't the Kopernio button actually say "Publisher website", as that's where the version of record and OA version is from? This is important because some people only want the publisher version of record, not a postprint/preprint, and may not click the Kopernio button if it says OA alternative.