Interpretation of Progress S-Curve without Schedule
Case-1 the actual overall actual progress value of reporting period is less than the overall early planned value but above the overall late planned value: the agreed baseline completion of Project may or may not get extended, all depends on the progress achieved on the planned critical path.
Case-2 the overall actual value reported is below the overall late planned value: does it mean that the agreed Project completion date is extended, or it depends on the progress on the critical path
Appreciate your kind thoughts....
Kannan
The volume of work completed is a good indication of progress overall but you need to be using something like Earned Duration or Earned Schedule to see the potential effect. These techniques forecast completion based on performance to date and have been shown to be reliable indicators, see: https://mosaicprojects.com.au/PMKI-SCH-040.php#Process2
However, this is different to the measure of progress on the critical path. You need both for a complete picture, but you also need to recognise the projected completion based on CPM is wildly optimisitic: https://mosaicprojects.com.au/PDF_Papers/P117_Why_Critical_Path_Scheduling_is_Wildly_Optimistic.pdf