I do not think there is a direct link between Medical and the Decision made, Third Status and Fourth lines appear in ECAS. I mean four months is not an indicator, I have seen people finish in 1 month after Medical results and others in 8 months. I think this period on the time line is the intersection between the final two processes,
Process (1) I do not think every VO in the world has a canadian doctor who understands Canadian Medical insurance system to review the medial exam results as the criteria for NON EDE means that your medical case should not create excessive demand on Canadian Health Insurance system more than the average Canadian Citizen "a Figure of USD 4,000 per year is the bench mark". This must be a centralized function in CIC and There must be a medical committee in CIC in Canada reviews all medical reports from all over the world. They should be able to clear Medical in 3-4 weeks (1 month). Bottom line, as long as they did not ask for further exams, Medical results are fine.
Process (2) As They will not process any application untill it is complete from all required documentation so why they are taking so long time. I think Processing invloves the longest steps which is the Security Checks. They will enquire from local police about your PCCs, talking to Interpol, talking to Anti Money laundry organizations and many local policy agencies to verify the accuracy of PCCs.
It depends on how many and which countries have you lived in more than 6 months and how many PCCs have you submitted d from what countries, which country you are originally from (Iraq, Egypt, Pakistan and Syria will take longer time due to local reasons), checking all your previous trips that you mentioned in your application, etc etc etc.
This process is the longest I think and it is out of their control and it the only explanation why different VO office aroun the world has different processing times as there are some local needed inputs. It normally takes a minimum of 4 months up till 12 months in some cases. This process starts before the medical from the point they say we started processing your application.
This is just my point of view and it may help you assess if your application will take more time or not, I know Mine will