Tasks group (not slot) takes on the length of the longest task, not it's sum

When dropping tasks one onto another in the calendar they make a group which length corresponds to the longest of the tasks in the group and not to the sum of the times durations of these tasks. So if I put three one-hour tasks onto each other they will have a length of one hour. If I put one hour task and then three five-minute ones on top of it it still has the length of one hour. Observe the gif. The expectation as a user for me would be that the overall length of the task group would be the sum of its parts