If I create a task in Inbox and then schedule it as all-day, it has no estimate. However, if I create a task in the calendar as an all-day, it will set a 24h estimate to it on my behalf. If I unschedule such task to complete it later, it will have a confusing 24h estimate indicator in the Inbox.
I don't need 24h estimate to be set automatically, as I don't mean it, when I create an all-day task in the calendar. A task scheduled to a specific day, but no time, means that I'm going to complete this task on that day at some point, not that the task will take the whole day to complete.
A task created in Inbox and then scheduled, should have the same attributes as a task created with scheduling. And similarly, task created with scheduling and then unscheduled, should have the same attributes as a task created in Inbox.