3 books a DAY? How about 3 books a month? Or 3 books a year? Only the most prolific authors have managed 3 books a month.
Something like 60/month seems like it'd be a little more reasonable to allow these legitimate upload waves though.
That would cause scammers to create new accounts, upload 60 books, hope to sell a few on the first few days until they get caught, then rinse and repeat.
Amazon will probably also monitor accounts who upload 3 books a day using some heuristic so that they can stop it before it becomes an issue.
Same way illustrators could publish their roughs and croquis as books, etc.
As those can be set with a 0$ price, and virtually no inventory issue, it feels like a practice that doesn't penalize either amazon, nor the author, nor the readers.
Amazon has a separate service within KDP for exactly that kind of serialization, [0] so while its true that KDP handles a wider range of books than just the novel-size works people seem to be thinking about, that particular example is probably an explicitly not-prioritized use case for regular “book” publishing on KDP.
[0] Kindle Vella: https://kdp.amazon.com/en_US/help/topic/GR2L4AHPMQ44HNQ7
- is copy pasted from another source or the internet
- respects copyright
- is written in the language it says it is
In graduate school nobody can understand each other's papers, so the colleges set up a massive list of formatting guidelines. The idea being the focus on formatting means you at least had to spend a minimum amount of effort.
Your friend might be part of the problem.
KDP “books” include “low-content books” (prompt journals, etc.), not just novels.