First, we see a turn arrow next to the "My Drive" text. Normally, in almost every OS or UI, this signals to the user that this is a control on which they can click, and which click will effect a change in the UI: most usually reveal another level of the information hierarchy. (The canonical example is in List View in the Mac OS Finder. Go ahead, try it now; I’ll wait.)
In this case, I clicked on it, because the principal investigator on our project said she has a file she wanted us to see in a subfolder on Google Drive. I heard "subfolder", so I (not unreasonably, I thought) tried to navigate to what looked like it’d be a subfolder, by clicking on the turn arrow.
As we can see in this video, clicking on the turn arrow does indeed turn the arrow. But that’s all it does. And then clicking on it again does nothing. The turn arrow remains in the "I’ve progressively displayed information" without ever having done so, and remains so smug in its certainty that you can’t unturn it.
Then, on a whim, I click on My Drive. To my surprise, this changes the information shown to the right. It’s fun to note that this breaks the interaction pattern of the Gmail web interface, where the Inbox view is the default view and clicking the top menu item, Inbox, shows that info. So, what was I looking at when the page first loaded? How do I get back to it?
So I click on "Shared with Me". That actually shows some of the files the PI was asking us to look at. Apparently, the mental model in the people she shared with — a separate information category — was not the same as what she saw — a subfolder.
But anyway, how do I get back to the stuff that was on the page when I logged in? My Drive? Nope. That control? No, that’s to upload files, not move up in the hierarchy (whatever that may be).
The Back button in the browser? Give it a try and what the hell? What is this "Activity" screen? (Note: I could not reproduce this, which is itself worrisome for QA.) Let’s try Back again. Okay, we’re back to where we started. Whew. Now about that turn arrow… nope. Still smug. I just must not get it.