Currently it's really hard to understand which features are GA and which BETA/ALPHA.
On some feature this is mentioned right below the feature heading on others somewhere in the text on some it's the last sentence.
Description of https://www.percona.com/doc/percona-server/5.7/management/data_at_rest_encryption.html#innodb_encrypt_tables is hard to read. By reading this text feature seems to be BETA quality, but some values for this option are ALPHA quality. Values and theirs description don't seem to be the part of the variable description. This variable might be better suited its own heading (Table Encryption?)