Verified on 4.6.0-0.nightly-2021-03-25-051145.  Invalid configs are not accepted.

$ oc get clusterversion
NAME      VERSION                             AVAILABLE   PROGRESSING   SINCE   STATUS
version   4.6.0-0.nightly-2021-03-25-051145   True        False         53m     Cluster version is 4.6.0-0.nightly-2021-03-25-051145

$ cat bad-ctrcfg.yaml 
apiVersion: machineconfiguration.openshift.io/v1
kind: ContainerRuntimeConfig
metadata:
 name: set-pids-limit
spec:
 machineConfigPoolSelector:
   matchLabels:
     pools.operator.machineconfiguration.openshift.io/worker: ""

$ oc create -f bad-ctrcfg.yaml 
The ContainerRuntimeConfig "set-pids-limit" is invalid: spec.containerRuntimeConfig: Required value
$ oc get kubeletconfig
No resources found.
$ oc -n openshift-machine-config-operator get kubeletconfig
No resources found.
$ cat << EOF > invalid-kubeletconfig.yaml
> apiVersion: machineconfiguration.openshift.io/v1
> kind: KubeletConfig
> metadata:
>   name: set-max-pods
> EOF
$ oc create -f invalid-kubeletconfig.yaml 
The KubeletConfig "set-max-pods" is invalid: spec: Required value

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (OpenShift Container Platform 4.6.25 bug fix update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:1153