includeFields not working as described in the documentation

I am looking to make some performance tweaks and am trying to reduce the fields down to only what is needed.

The includeFields parameter has been renamed to includeOptionalFields. The includeFields parameter now means “include only these fields” where in the past it meant “please add these fields you wouldn’t normally include.” This was changed to be consistent with the cloud provider API.

within the API documentation is makes reference to the above change to includeFields however it still operates with the old behavior and does not “include only these fields”.

For example includeFields=lastViewedAt still contains the summary however, excludeFields=summary removes it.