Yup, they call it "commingling". So even if you make sure it says "sold by and ships from Amazon", and Amazon itself only buys from legitimate vendors, you could still wind up with a counterfeit item introduced by a third party seller.
That may have been true once, but no longer thanks to "commingling":
"Sellers on Amazon can pool their goods with the same exact goods offered by Amazon itself, a practice known as commingling. This has advantages for sellers — less processing is needed, so it’s cheaper — but it also explains how Amazon can unknowingly ship counterfeits despite getting stock directly from the printer."
It looks like when the script fed the titles into the Goodreads API, it picks the most common (popular?) book with that title. Since the subtitles were stripped out it got confused.
In the original thread, the two books were:
-Linear Algebra, A First Course by Kutler
-A Concise Introduction to Linear Algebra by Schay
both in JabavuAdams' post.
Then there was a mention of the Linear B language elsewhere