multicluster-engine.v2.10.0
advanced-cluster-management.v2.15.0

Deployed an OCP4.20  cluster with IBI.

The clusterinstance had the following for additionalNTPSources:

spec:
  additionalNTPSources:
    - clock.redhat.com
    - 1.ca.pool.ntp.org 

The target deployed with no issues.

The created ICI  has this as expected:

spec:
  additionalNTPSources:
    - clock.redhat.com
    - 1.ca.pool.ntp.org 

The chrony.conf on the target has the expected entries:

cat /etc/chrony.conf pool 0.rhel.pool.ntp.org iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
logdir /var/log/chrony
server clock.redhat.com iburst
server 1.ca.pool.ntp.org iburst

With that the running instance of chrony didn't show the expected entries among sources. To actually get the entries I had to manually restart the cronyd service.