Your ghost update can also be a PPR request. But unfortunately mine wasn't. When I called they said "your background is half way done", dont know what that means.
As I understand, the background check has not two or three, but a decent number of different checks. Mine also wasn't a PPR request, cause they said that some security checks are still in progress. What I got from browsing the forum, average wait time from ghost update to PPR ranges from one day to one month being the longest.
There were a couple of people who have waited for several months from the first ghost update, but i guess is when they fall under security screening.
Anyways, I really think that your ghost update also means passing eligibility.