Citing books: international edition or the original edition?
A citation represents a source. Authors should cite sources they used. (I'm sure many don't, but that's besides the point.) Your assumption is correct:

one should cite the version/edition that they have access to

As you rightly note, citing an edition with limited circulation may cause readers difficulty. By contrast, citing an unseen edition will surely cause readers more difficulty: Authors cannot know whether an unseen edition contains the same material. They certainly cannot know whether page numbers remain consistent.
As a compromise, authors can cite section numbers, perhaps even noting the section name when inconsistencies are known, e.g., because tables of contents (available via Amazon, Google Books, or publishers, for instance) differ.
Authors may sometimes have access to multiple editions (e.g., via Amazon or Google Books, for instance), allowing a more widely cited edition to be cited.