aurora_oom_response value is empty

Hello

Following the aws link https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/CHAP_Troubleshooting.html

we decided to enable the aurora_oom_response parameter with the value print, tune, decline, kill_query in our DB clusters' parameter groups but we have noticed that the value appears as empty when using the mysql client:

mysql> show global variables like '%oom%';
+---------------------+-------+
| Variable_name       | Value |
+---------------------+-------+
| aurora_oom_response |       |
+---------------------+-------+
1 row in set (0.00 sec)

mysql> 

We even tried rebooting the instances but the value still shows as empty in mysql client although is clearly setup in the right Parameter groups (cluster and instance). Is this a bug in Aurora? the engine used is 5.7 version 2.11 Thanks!