I believe the main concern here, from dealing with clients that have mandated no PII in logs, is both authorisation as well as control. If it’s in your service logs, then it could be in your Splunk logs, it could be in a storage repository and it could be in your requests that you send to the service provider to troubleshoot some issue.

Unless there is a valid use case for logging PII (and I can’t think of any which can’t be engineered around) then I think it’s best to avoid it in principle.

I think of it as the same as logging passwords, keys or tokens.