The setting must not be making it into the column. How columns are merged from config into EventLists (Agenda is an EventList which is a Grid) changed recently (after 5.1.4)
Try setting it in the debugger after you have shown it:
myCalendar.activeView.columns.first.autoHeight = true;
If t his works, then you can work around it until the fixed version comes out in a few days.
The ticket is fixed and in the codebase