Audited for what telemetry is transmitted from an iPhone or Mac during use, what information is possible to harvest by a third party app, and whether or not purpose-made experimental data is made available to advertisers.

It looks like no official (that is, authorized by Apple) audits have been done, at least that I can see. But privacy research firms have done it, and the consensus appears to be that Apple is not great, but better than Google, Amazon, and Facebook. For what it’s worth.