It’s sort of funny that this kind of thing could be, not just something that they will probably just get away with, but totally uncontested and not even surprising really. Just sorta like, yeah, obviously you don’t own your library and they’ll cut off access to it whenever they want!
Access to your library continues to be available with free apps on phone, or Windows, or a newer Kindle as well as any browser, so the loss of support of 14 year old mobile devices doesn’t seem like huge news. There can’t be too many still in use even.