Eric, you marked this as UI>SignIn, but from the description, I would assume that this has to do with the progress bar in the primary toolbar.  Could you add more details about what the actual issue is that Apple pointed out to us?

The bug came from the signin part of the document, so I'm assuming there is another progress bar on signin somewhere.

To pinkertong for details, as he was in the meeting.

This was said about the sign-in flow, not our main progress bar. That's all i know.

cc'ing Identity folks. 

Do we have a screen shot?
There is an activity indicator bar in SSO when adding a new account. I don't see any issue.
There is an activity indicator circle after selecting the account, while opening the user consent. I don't see any issue.
I would need more context.