I think I may have deduced the answer to the dilemma of the divergent book directories.
From what I've found I can't be certain so it's only a theory, like evolution, but my best guess is that there are two almost completely different collections of stories with the exact same title.
First, there is the “original” version, our selection for this month, with the contents fantasyfan listed. From my searching I can’t find hardly anything on this version, only some various old-looking book covers in image searches or old copies for sell with no info except that it’s around 250 pages. Because of its scant presence online (so far as I’ve been able to tell), I am thinking that perhaps this version is out of print and only old copies exist.
Second, there is the “other” version, with the contents I listed. Looking into the ebook version available on Amazon U.K., it gives its first printing as well as its “introduction” and “selection” copyrights as 2005, and the author of the intro discusses selecting the stories for the book. So this book seems to have been put together and printed for the first time in the 2000s, with a blithe disregard to giving itself the exact same title as a previous different collection. This version often has a cover of half a boy’s face and is around 350 pages, and of course this one is still in print. Anyone buying the ebook will be buying this “other” version, and some pbooks are this version as well.
issybird earlier complained about books needing to have just one title, but here we have the opposite - too many books having the same title! It's such an odd turn of events that couldn't have been predicted. And strangely enough, the (wrong) ebook only being available in the U.K. seems to have worked out in our favour since it prevented most people from acquiring it unawares. And regardless of which collection one acquires, it will contain at least some stories from our monthly selection, and other stories that can be enjoyed as well, so it's win-win.
From what I can tell by looking at the table of contents in "look now" on Amazon, "The Best of Frank O'Connor" ebook doesn't include as many stories of the “original” version as it does of the “other” version, but it does include more than half, so that’s something. I didn't count the number but it seemed like maybe 5-10 of the stories in our selection this month were missing from it. I know I’ve done a good bit of looking around for all this, but in for a penny, in for a pound. I am however finished with looking for an ebook way of getting all the stories; I just sucked it up and ordered an old copy of the pbook, and looking forward to it. I am going to edit the first post in the discussion thread to remove the wrong version links and to include the correct contents.