I also checked AMD's page, and while the new driver package is not available for the RX 590/580/570/560/470/..., it
is listed for the RX 5700/XT.
So there are multiple options:
- AMD is doing a staggered launch for different GPUs, either to balance the load on their servers, or because there are still problems for some GPUs that they're trying to iron out;
- the listings for some GPUs have been left out unintentionally, and they need to fix their website/database; or
- changes on their support pages haven't propagated to all products for some reason - maybe a reverse proxy is still serving the old pages.
The fact that even the Radeon Settings update check doesn't offer the new version for RX 570 would imply point 1. Then again, if it's a database data entry error, it could effect the website and the settings app equally.