Related command
az vmss create
az vmss update-instances

Is your feature request related to a problem? Please describe.
After including the Guest Attestation by default feature in the latest version, I discovered a miss from the original request specification. For the VMSS scenario, the current behavior is that the VMSS model reflects the MSI enablement and Guest Attestation Extension installation, but the instances are not actually updated with the model. This is because by default, VMSS has the upgrade policy set to manual. This blocks the actual VM instances of VMSS to actually get the Trusted Launch features.

Describe the solution you'd like
In order to apply the updated VMSS model to the instances, we need to accomplish the equivalent of the following command AFTER MSI and the extension is updated in the VMSS model in the convenience layer:

az vmss update-instances --resource-group "rgname" --name "vmssName" --instance-ids *

Additional context
This was a miss from the original request