I think its important to clarify a few things. The article is noting that they blocked the downloading of books that use "Kindle Unlimited" which is a subscription, that runs $10 a month, for unlimited of select Kindle titles. Think of Kindle Unlimited as the book equivalent to Spotify Premium.

You can still download and un-DRM books that you buy individually from Amazon directly. This is an important distinction. Because you "own" the book you buy directly. You don't own titles through Kindle Unlimited, you are borrowing them.

The restriction from allowing the downloaded books on this service actually makes a lot more sense when you understand the service. This is no different than we see from any other service where you pay a monthly fee for access to content while maintaining an active subscription. For example you can download songs with Spotify, but they automatically expire after 30 days unless they "phone home" to confirm you still have a subscription. Netflix, HBO, Hulu, etc all let you download movies now, but they expire unless you maintain a subscription.

You don't own any of this content, it is just lent to you for the duration of an active subscription. Kindle Unlimited is no different, but for books.

The important part is that nothing has changed for books purchased directly from Amazon individually. This change is only for the Kindle Unlimited service.