I don't know why you are getting downvoted, you present valid objections to the assumption that everything will always go smoothly. Education should be highly fault-tolerant instead of punishing failure which might not even have been in your power to prevent.
The course has presumably been designed so that a motivated and intelligent student can understand it in this time.
But what happens when life interferes with a student's plans? I can think of lots of reasons why a student may be distracted by legitimate life events in this period of time, e.g. illness, or a family wedding/birth/death etc.
Online courses do give you the flexibility to work around things like this. They also allow people with full time jobs to access the material at a pace which suits them.