Is it possible to limit SEPM to GUP transfer and communication by the time of the days? such as no updates in business hours 9AM - 5PM? I think the answer is no, but I still would like to confirm.
Not possible. You can throttle bandwidth but not possible to set a schedule.
How client computers receive content updates
http://www.symantec.com/docs/HOWTO80888
Yes it's not possible,
See this thread
https://www-secure.symantec.com/connect/forums/schedule-time-gup-get-content-sepm
See this articles