Does Argo CD automated sync policy work with helm repository?
Checking documentation https://argo-cd-docs.readthedocs.io/en/latest/user-guide/auto_sync/ it mentions only Git repository. But in project settings one can set automated sync policy even for helm repository.
What I expect for automated sync for helm repositories: Application should be synced once new, higher version of helm chart appears in Helm repository.
ArgoCD supports Helm repositories just fine for sync purposes. However it doesn't check for "newer" versions as you say.
You might want to look at https://argocd-image-updater.readthedocs.io/en/stable/ which does the same thing for container images (And given OCI support, maybe at some point will also do what you ask)