Apple's Policy on Apps Pulled from the App Store

I was troubled to find that when an app is pulled from the storefront, it is not always still available to download if you have already purchased the app. I was under the assumption that if an app is pulled, you still have the ability to download anything you've paid for (whether they work with future versions of iOS is another story).

Has it always been this way? This seems unbelievably anti-consumer, and terribly troubling. Do many other digital storefronts have the same type of policy?

I was under the impression they would remain in your available downloads regardless of whether they were removed from the store-front or not. This is troubling. I'll have to make sure I back up EVERY single app to my computer so they can't pull this on me again.

I have been purchasing apps for years now and I have had some observations.. From experience, this is what I believe.

If an app is pulled due to unpopularity or because it's has a new version (such as that weird OneNote change over), than it can still be found in purchased, and thus can be deleted and downloaded again, even on other devices with your Apple ID.
If an app is pulled due to legal reasons (such as emulators, like GBA4iOS, rest in peace, lol), than it will also be deleted from purchased and once it is deleted off your device, it cant be downloaded again.

To the best of my knowledge, any app you purchase will be available to redownload, as long as it's developer is still paying to be a part of the Apple Developer Program. If they stop paying, their apps are pulled, and you can't redownload them.