Why using instance firewall instead of relaying on security lists?

[SafaAlfulaij]

As written in the title.
I see that the firewall is being set on the instance and PostgreSQL level, together with security lists.
Isn't security lists enough? I believe that if someone lost access to a network ip, it would take more time to enter maintenance mode and add the new ip (in case of public subnet).

[paihari]

Thanks for the terra files, works like designed. Like stated earlier by @SafaAlfulaij . It works fine in the private subnet.
But If i have application(in my test tested my pgadmin4) peer public subnet in the same VCN and have configured needed ingress/egress. The connection is not allowed. The scenario is close to the real world.

What need to be done, can you suggest the changes to be done to the code