What is the logic for changing the cursor on hover in Google web apps?

Question

Google

By what principle in Google sites / applications is it determined whether the cursor will change to "hand-with-outstretched-finger" on hover? Let's take, for example, Inbox. In the header, the menu icon - the cursor changes, the application icon, Hangouts, the user's photo - does not change, although it's all clickable too.
We go further - Google Translate. Here, on almost all buttons, the cursor does not change, except for the "clear" button (it has a cross in the upper right corner of the field).
What's the logic here? I would like to discuss this topic, because. it is not always clear how to do it.

Answer 1

The finger is placed when there is a link to another page. And all UI elements that work on this page are simply highlighted by the cursor. I think so. I don't see it otherwise.
About the clear button, well, xs, maybe put a hand cursor everywhere?