When it comes to RDS, you may not see OFF as an option because doing automated backups requires binary logging.
Inside the mysql.rds_set_configuration say this
For RDS for MySQL, NULL means binary logs are not retained (0 hours).
For Aurora MySQL, NULL means binary logs are cleaned up lazily. Aurora
MySQL binary logs might remain in the system for a certain period,
usually not longer than a day.
If you want to logically disable binary logging, you can set that manually like this
mysql> CALL mysql.rds_set_configuration('binlog retention hours', NULL);
NULL is the default retention hours. See AWS Docs on this. Also, I wrote about this 4 years ago (See my answer to enabling BINARY LOG on AWS RDS MySQL)
CAPTAIN's LOG SUPPLEMENTAL
Personally, I have seen the OFF option when deploying Aurora. That's because Aurora has other redundancy mechanisms which do not need binary logging. You have the option list
ROW, STATEMENT, MIXED, OFF where
OFF is the default for Aurora.
Setting binlog_format to something other than
OFF in the DB Parameter Group allows you to set up MySQL Replication from Aurora to external servers.
With RDS, OFF should never appear as an option for the reasons I just stated.