Why is 3.x beta?

The [release notes](https://pecl.php.net/package-changelog.php?package=memcache) of versions 4.x and 8.x say:

> - Support for PHP 5.x has been removed, please use memcache extension ver. 3.x 

Why then is every 3.x release marked as beta? Can [3.0.9](https://github.com/websupport-sk/pecl-memcache/issues/63) be marked stable when it is released?