[Cinisajoy]

I couldn't follow that blog.
Now what I can tell you that I know is a fact.
Books in Kindle Unlimited get a choice of countdown deals or 5 free days in a 90 day period.
If books are not in Kindle Unlimited, then authors do not have the option of free.
How they do this is they put the book at Kobo, B&N, Google or a combination of them for free and hope Amazon price matches.
Amazon can do one of three things. Price-match, not price-match or send a letter to the publisher that they are in violation of the TOS and their book can be pulled.

Yes, when you upload a book to Amazon, you agree not to price lower anywhere else.

Note: The authors/publishers in Kindle Unlimited actual check Select which means they cannot publish the book anywhere else as long as they are in Select.
Select is for 90 days, then the author can choose either Select again or uncheck it and can then publish elsewhere but they lose those free or countdown days.