I don't understand how any such comparative study can be conclusive without actually auditing those "major tech companies", it's more self-assuring clickbait th

I don't understand how any such comparative study can be conclusive without actually auditing those "major tech companies", it's more self-assuring clickbait than anything else. I'd say one could draw some pretty close conclusions for a company like facebook, as their products needs to interface not only with the user but also other facilities to gain data, and the assumption of interconnecting this data could give you a good foundation. But to then reach a comparable insight on how much data Apple collects, a company where the typical user is using Hardware provided by Apple, an OS by Apple, logged-in using an Apple ID and using a multitude of applications and services which all use SSO connecting to Apple servers....?