New Calendar entry -> All Day Event -> Alert time (can't change)

When adding a new calendar entry, and setting it to be an All-Day Event, the available alert times are as follows:

On day of event (09:00)

1 day before (09:00)

2 days before (09:00)

1 week before

How can I change these times, because 9am is useless for me, I need it to be much earlier, say 7:45, or 08:00.

I've already gone into settings -> Reminders and updated that time there, but calendar still shows the 09:00 value, and then inside Settings -> Calendar, there is a 'Default alert times' but again, the values are exactly the same as mentioned above. Why can't I change these?

Here is the Settings -> Calendar -> Default Alert times for All-Day Events. There is no way to change these values.

And here is the Settings -> Reminders with the alert set to 8am.

Am I missing something, or have Apple left out a pretty basic feature..?