The charging settings on this car are a bit buggy and confusing.
For your situation, you will have to set a departure time for each day of the week that you want the car to charge. Then also set the off-peak hours. The car will ignore the departure time and use your off-peak schedule to start charging.
Please let me know if your car also fails to turn off the instrument cluster after it begins scheduled charging.
For anyone who actually does want departure-time charging instead of off-peak charging, I did find a work-around. Somehow by toggling the charging schedule settings in their Android app, I was able to completely clear the off-peak times. It now just shows a blank "--" line through all the off-peak times. This has enabled the departure-time menu to actually work for me. The system is still not very accurate - it usually finishes charging an hour or more before actual departure but at least it does reliably charge the car each night.
The reason why someone may prefer departure charging over off-peak charging, might be to maximize time spent charging on solar for example. If you depart during daytime, the car would get as much charging done as possible while the sun is up instead of completing the entire charge early during the night.