Good news: I also reported this to Asana Support, and they said that the new time-tracking custom field in Portfolios > Workload has only been rolled out to a few organization spaces up to this point. For users who are not yet seeing this aspect of the new time-tracking features, it should be coming soon. 
FYI on this @Rebecca_McGrath, Aaannddd Release 1 has now been fully rolled out to all Business and Enterprise users. 