How do db.t4g instances burst? No CPU Credit in monitoring.

I'm testing some db.t4g instances and noticed that they do not have metrics for "CPU Credit Usage" and "CPU Credit Balance" even though they are "burstable". The db.t3 instances have these metrics.

The announcement https://aws.amazon.com/about-aws/whats-new/2021/09/amazon-rds-t4g-mysql-mariadb-postgresql/?nc1=h_ls only says that "T4g is the next generation burstable general-purpose DB instance type that provides a baseline level of CPU performance, with the ability to burst CPU usage at any time for as long as required.". The links are to the EC2 page which does mention credits. The RDS Instance Type page https://aws.amazon.com/de/rds/instance-types/ does not show anything about t4g instances.

So how does bursting in these instance types work?