In emails and inbox notifications the relative timestamps were converted to absolute timestamps about a year ago(sic! It was in Oct '14).
These days (Oct '15) I'm often checking review queues. Most of the items in the close and reopen queues are fairly recent. Therefore the timestamps on those pages are relative. Often questions by new users start out relatively bad, but are then improved. To understand the current state it is helpful to understand how we got there. If the question, the edits, early answers, and all comments are labelled as appeared "2 hours ago", we cannot see the dependency between the older versions of the question, the edits and the time answers and comments appeared.
I would hope that moderators at least get a full chronology of everything that happened to a question. We could have it all for reviewers if there were no relative (and thus inaccurate) timestamps. If all were the ISO 8601, including seconds reviewing would often be a bit easier.
Actually I am surprised that this has not been asked before. But even looking for just "relative timestamp" I could only see discussions and alleged bug-reports about inaccurate relative timestamps. This Q is about a different kind of inaccuracy: The fact that two times "2 hours ago" doesn't tell me about the chronological order of those two events.