The auto planning feature does not work when a resource is re-unassigned work

Reporting for v 7.0.2

I have the Auto-planning check box selected, as shown below.


In an experiment, I selected task-5 and deleted the resource, which was assigned at 100% rate.
I again added the same developer, and assigned 40 hours of work at 20% rate.
Then I saved the task.

Since the auto plan check box was selected, I expected the task to be recalculated automatically.
But this did not happen.
Finally I had to press the Calculate activities planning button manually.
The screenshot shows the final result.

Thus there is a bug in Pr5ojeQtor: The auto-recalculation checkbox does not work in some cases.

I will test this again, and revert.

@check box being active only when visible:
I am sorry, but I did not understand this caution.
I was on the same screen (but working in the lower half, where I can change the assignment).

Which are the other use cases when we are NOT on this page, and therefore the recalculation does not automatically happen?
Our PMs must understand this tip properly.

I checked this feature, and confirmed that it works fine.

However, during the testing, I noticed that tasks for a resource were overlapping. This was unusual, so I investigated by right-clicking on each task. I found that the resource (Akshath Hegde) was assigned 100% to each task, yet ProjeQtor split his daily hours among three tasks.

The screenshots below explain this situation:



So the question is, how exactly did ProjeQtor reduce the number of hours on a daily basis (from a constant 8 hours/day)?
Does this method ensure that these three tasks are finished in least amount of time? (Two of the three tasks were on critical path.)