Nothing on Amazon is going to work like books on Amazon do.
Amazon is, originally and primarily, a bookstore. Amazon has long-established direct contracts with all book publishers (and in fact, a stranglehold over those publishers.) Any time you see a book listed on Amazon, it's a book sold by Amazon, attained directly from one of these publishers.
AFAIK no third-party sellers are even allowed to sell "books" Fulfilled By Amazon; if you see a third-party FBA "book" on Amazon, it's because the seller slipped it in under some category other than "books." (The "novelties" and "calendars" sections are often abused for this.)
But for categories other than books, Amazon never built up this same direct logistical pipeline to suppliers, let alone the sort of stranglehold over suppliers in other categories that they have over book suppliers. So Amazon doesn't have the ability to force constant, even, predictable supply with contractually-set pricing in other categories, the way they can with books.
Often, this means that Amazon's first-party supply chain for something, might just run out of that thing entirely.
Part of the reason the FBA program exists is that it allows Amazon to take advantage of third parties' connections to suppliers to compensate for their own supply-chain deficits. Amazon-the-asset-holder might have run out of e.g. Kleenex, but that doesn't mean that Amazon-the-site or Amazon-the-pool-of-warehouses has run out of Kleenex, because Amazon has allowed some third-party FBA seller to stock stuff in their warehouses, and that seller happens to have brought in some stock that have the UPC code for Kleenex. So hey, there you go, we have Kleenex after all! Only now Amazon has to follow the seller's dictates on pricing and discounts — and your experience on availability (unless/until first-party supply comes back) will be dictated by the seller's (usually much-less-predictable) ability+desire to resupply.
There are situations where this model actually makes sense! Some mid-sized OEMs that Amazon doesn't feel are worth their while to engage with directly, instead sell their products directly through Amazon as FBA sellers. In these cases, buying the product on Amazon is just like buying the product through the seller's website, but you get it faster because it's already in an Amazon warehouse.
That said, despite FBA having times where it makes a lot of sense, I also find Amazon Marketplace distinctly baffling. A thing sold by a third party, shipped by that third party, with returns handled by that third party, shouldn't be able to be conflated with an Amazon.com/Amazon FBA listing just because of a shared UPC code! Those are two very distinct experiences and are not fungible, and it's bizarre to pretty much everyone I know that Amazon has tried to conflate them.