Here is what I know:
It can take several days for the PIN emails to be sent out. DH and I both received the April-August PIN 3 days after they started rolling out.
Here is what I don't know:
I don't know if all of the PINs get added to the accounts at the same time and it's just the emails that go out differently.
OR
if the PINs get added to accounts on different days and the emails go out on the same day the PIN gets added.
I am hoping that they get added to accounts over the course of several days (since I called yesterday and didn't have one), but no way to know.