The benefit is as OP said: it bypasses corporate firewalls because it's a google doc.
Although I can only reproduce this redirect page in a published doc page[0], not in a pdf export (unless there's another way to download pdf via url trickery)
> edit: you can reuse the URL to download the export. tested on another network. it expires fairly quickly though, within a couple minutes it seems.
(thanks for the test)
So it's clearly not a possible real vector, and actually they thought about it being a possible vector, otherwise they would not have put the expiration.
Although I can only reproduce this redirect page in a published doc page[0], not in a pdf export (unless there's another way to download pdf via url trickery)
0: https://docs.google.com/document/d/e/2PACX-1vR4O-8LwvUPNOcwH...