Thank you for reaching out. Your understanding is right that views created on external tables for users who do not have access to the underlying tables.
For a user to access the view, they needed to be granted USAGE permission on the external schema. This is currently a limitation and we have a feature request in place to address this concern. However, we do not have an ETA for the feature at this point of time.
I request you to follow below blogs for information on new features.
 What's new: https://aws.amazon.com/redshift/whats-new/
We apologize for the inconvenience.
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