[Bug] Updating existing nodegroup bails out due to regex validation failure

[cg-cri-gl]

What were you trying to accomplish?

Trying to scale up a nodegroup, where both it and the EKS cluster were not deployed using eksctl.
The command i ran is:
eksctl scale nodegroup --cluster eks-cluster --nodes=3 --name on_demand-20250709145022911400000011

What happened?

Error: validation for on_demand-20250709145022911400000011 failed, name must satisfy regular expression pattern: [a-zA-Z][-a-zA-Z0-9]*
which is due to the _ in the nodegroup's name.

How to reproduce it?

`eksctl scale nodegroup .... --nodegroup-name_containing_underscores

Logs
error message : Error: validation for on_demand-20250709145022911400000011 failed, name must satisfy regular expression pattern: [a-zA-Z][-a-zA-Z0-9]*

Anything else we need to know?

Versions

eksctl version: 0.220.0
kubectl version: v1.33.1
OS: linux

[github-actions]

Hello cg-cri-gl 👋 Thank you for opening an issue in eksctl project. The team will review the issue and aim to respond within 1-5 business days. Meanwhile, please read about the Contribution and Code of Conduct guidelines here. You can find out more information about eksctl on our website