Earlier quoted context omitted.
The explanation in the other comment is also correct. When you go from drive.google.com to googleusercontent.com to download a file, this historically worked by using third-party cookies to verify that you were authorized to download the file. When Safari dropped support for third-party cookies they added a new flow which uses link decoration instead, but only use this flow when they think the browser doesn't support…
It seems obvious to me why they don't use that for everyone, and it has nothing to do with security.
* Security: as described above
* Efficiency: the method used for Safari requires more server resources
* Performance: the method used for Safari is slower
What is the reason that seems obvious to you?