Now, it doesn't matter if your competition is selling thirty books an hour or three books a decade. The books are available to be found either way and your book gets lost in the vast sea of books, regardless of how well they sell.
There is a big difference between available to found and likely to be found.
I think Timothy's point is that books that have sold little or nothing in recent months are really only findable in a practical sense if you search by specific author and title. In other words, to find them, you need to already know they exist. If you search a genre or even a subgenre, such books, if they get listed at all, will be so many pages in that you will never see them.
Example:
Look at the Kootenai Trees. I know about this book only because it was published by another Bill Hiatt in 1976. It does show up in search results for my name if you search in books. It shows up if you search by title using the exact title. But if I just type in a word like Kootenai, which can't be that common, I get 22 pages of results, none of which is the target book. This search does produce things as obscure as leatherbound environmental impact statements related to the Kootenai National Forest in Idaho, even though they aren't currently available. But it doesn't take me to
Look at the Kootenai Trees, and at the end, it says "No results for kootenai in Books.
Try checking your spelling or use more general terms." This is odd, since it found me some results. But it didn't consider that particular one worth reporting.
You can bet the book isn't going to show up spontaneously anywhere else, either. The only way it shows is by author search or be relatively accurate title search.
Another example is an author I knew well when I first started. (I won't mention the name.) She was prominent in romance. Searching for her by name shows a lot of irrelevant stuff and two advice to writers books she published. Clicking on her name takes me to an author page where some of the romances appear. (They are generally in the 2 million or so bracket because she hasn't been active recently.) The fact that they didn't show up in an author search is telling, though.
Third example: One of my old shorts, "Angel Feather," appears erratically in searches. I think it sold one and now is back, but until recently, it didn't always appear in author searches. And unlike the author in the second example, I'm still active. But that particular title was in the process of disappearing.
In other words, there are a lot of books on Amazon that will show up only if you know exactly what you're looking for. Even an author search may not always do the trick. An exact title search will do. Looking at the author page will do it, though it will be hidden at first.
Are such books in real competition with us? No. They're in the abyss. Unless you know they're there, you're likely never find them.
So yeah, technically saturated, but only a small part of the product is really accessible.