It is a conscious design decision. It has a huge advantage of not having to manually correct notification times of tasks after plan changes. So this tool is best suited to people who:
- live an active life and try various things
- often change plans and adjust to changing conditions to get the most out of them
- understand that they can achieve more if they make an effort to think and plan for the future
Tap a task and use buttons that appear on the toolbar at the bottom of the screen to change its duration or move it up and down. If you edit a task you can change the default duration (used at the moment of adding the task to the plan), so that you don't need to use +/- every time. Long-pressing +/- will bring up a popup making longer time adjustments more convenient (you don't need to tap +/- many times).
Reminders are set automatically according to the plan. The first task will have the alarm set to 00:00 (12 AM). Subsequent tasks have alarms set to their start times displayed.
It's shown in this help video:
https://www.youtube.com/watch?v=0MSc4OVfc9U