this can be explained that this may be not egress out of AWS, but egress out of S3 system itself.

S3 is a block storage, so retrieving an object for such a high availability and high perf service means it tries to pull some X block of data and cache it before sending through the socket.

That X block of data is out of internal S3 storage, just not sent through the bigger Internet egress subsystem.

So technically aws may argue this is egress for s3, just not for aws