What happen?

In the PKG file/runtime/kubernetes kubeadm/common feature in constant DefaultKubeadmConfig in the go feature-gates have default values, but I don't want this field

According to The website https://v1-27.docs.kubernetes.io/docs/tasks/tls/certificate-rotation/ The document kube - controller - The manager process accepts an argument --cluster-signing-duration (--experimental-cluster-signing-duration prior to 1.19) that controls how long certificates will be issued for.
But --experimental-cluster-signing-duration is also defined in the constant DefaultKubeadmConfig

This part of the code combines the constants with the rendered kubeadmconfig