Oauth2 REST API calls towards wrong endpoint are returning 401 instead of 404

Issue Summary

When sending a REST API request authenticated using Oauth2 (3LO) to a mispelled/wrong REST API endpoint, status code 401 (unauthorized) is returned instead of 404 (not found).

This is misleading since the customers think the authentication is broken instead of trying to check whether the endpoint they are using is correct.

Steps to Reproduce

1. Send a REST API call toward the https://api.atlassian.com/ex/confluence/[CLOUD-ID]/wiki/rest/api/group?... endpoint
2. See that the request is successful.
3. Now add an extra 's' to the endpoint so that's "groups" instead of "group" https://api.atlassian.com/ex/confluence/[CLOUD-ID]/wiki/rest/api/groups?....

Expected Results

Since the endpoint is wrong/misspelled, we expect to get 404 - Not found

Actual Results

Status code 401 - Unauthorized is returned instead

Workaround

No workaround available at the moment.