No, a version of "5.0.67inode" should pass the version comparison. It's using the php function version_compare, and the requirement is 5.0. Using version_compare, 5.0.67inode > 5.0 and so it passes.
What is the actual value being returned by $wpdb->db_version()? What do you get if you call mysql_get_server_info() or mysqli_get_server_info()?