The documentation appears to be contradictory.
https://documentation.commvault.com/2024e/expert/rest_api_get_data_set.html
GET /CustomReportsEngine/rest/reportsplusengine/datasets/<datasetID>/data
Host: <host name>
Accept: application/xml
Authtoken: <authentication token>
When I attempt to use a bearer token, I get 401 not authenticated.