Because due to popular request we have been using Joomla!'s own extensions updater to provide updates to our software since Akeeba Backup 3.11.1. Unfortunately, among other problems, Joomla! does not understand the difference between a stable and a testing release. As a result it will suggest upgrading to the RC release. Since this problem comes from Joomla! itself we are unable to provide a solution.
Please note that before Akeeba Backup 3.11.1 we were using our own Akeeba Live Update which was much better and didn't have any of these problems. However, it would not allow our clients to update our software through Joomla!'s extensions manager or third party services (e.g. Watchful). This was a major problem with our clients managing more than a handful of sites, so we had to give in and switch to the badly written, misbehaving, completely brain-dead sorry excuse of an updater that is Joomla!'s extensions updater...
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!