This seems like a pretty poor implementation on Apple's app store's handling of out of date app installation. I believe there is a workaround where you can use an online version of the app store to first trigger an app download to your iphone, which would then transition it into that "re-download from cloud" state which lets you get an older version.
I've successfully installed an ancient version of iTunes for Windows to associate apps to my account and that method worked for a while, until Youtube pulled support for the version of the Youtube app that the old iPad I got used last. The web player is dog slow, so the iPad is pretty much a fancy glass eBook reader now.
