A standard email send seem a little confusing at the point of send, specifically the start and end dates.
For example, a user adds a dynamic segment to a customer journey, adds the email, fills out the details. When it comes to the method of sending though, it's not clear what the trigger is. Even when they're made aware of the start and end dates of journeys, they're having to make a decision which to them is irrelevent to sending the email. Users don't care what the start and end date is, they just want to send the email at this point but there's a decision of what dates do i put in? If they add an hour gap, there's potential for a large send to not complete. If they add in a day gap, there's potential for their dynamic list to change and more people are emailed than they intended.
For automations, dates are fine, for one of sends, they need to be trained as to what dates to add in and why. That seems like added complexity.