It's allegedly a result of how Calibre manages tags in order to display covers but still feels deeply wrong.
Long thread here: https://www.mobileread.com/forums/showthread.php?t=340936
There are two main tag values for Kindle books: EBOK and PDOC.
EBOK is intended for store content. (ebooks) PDOC is intended for user content. (personal documents)
In the past, only EBOK got cover thumbnails. So Calibre tagged books as ebok to get cover thumbnails.
This changed in a relatively recent firmware update for 7th gen and later Kindles, so now PDOC tagged books get cover thumbnails too. (Sept 2022)
I assume that Amazon just looks at the EBOK tag, assumes its an expired loan or something, and deletes it. Since that thread says only EBOKs get deleted. Calibre still tags as EBOK by default. A possible solution is to tag as PDOC instead. That thread mentions the problem started in 7/2021
I think you should reconsider "the benefit of the doubt".
I remember thinking similar things in the 90's with respect to microsoft.
I was talking to an ex-microsoft coworker about how windows would break compatibility with some 3rd party software. I said "engineers are under pressure to get some feature out, and they don't know how it affects every bit of software out there" or something", giving the benefit of the doubt to microsoft.
But he told me not to be naive, "microsoft would have meetings... How can we control this, how can we own this"
At the time that was a joke, we didn't care what MS Excel was, and then, for years, we didn't know anything other than Excel.