Hi, just to add another justification why this feature is needed:
When you are evaluating the call center, you need to know at what time of the day, you have too few agents that are causing the SLA to be low. For example, at lunch time. Other cause can be that the agent are log in late, etc.. So if you have the SLA per hour, you can focus the efort to improve the worse ours first.
Same thing can be per day of the week, example, weekends.