Customers often leverage section models to schedule content to publish to their site at a later date. However, when a customer needs to make a scheduled update to said content entry (ex. they want to change a few words in 24 hours) - the content reverts to its first state of scheduled and no longer appears on the site. This is expected behavior as scheduling applies to the entire entry/can't pinpoint changes that have been made.
The solution is to duplicate the entry so the only changes you need to make is adding scheduling and making any content changes needed, which works for most customers, but on the other hand, can see where keeping 1 content entry and scheduling an update to the same content entry can be preferred!