I finally have official confirmation from Samsung as to the issue of video auto-play. It does not exist on the Galaxy S6. I have taken the liberty of posting the appropriate section(s) from an email I received addressing the issue.
"Thank you for taking the time to contact us at Samsung Technical Support. We always appreciate hearing from our customers.
I understand that you want to know if there is option to auto play the recorded or downloaded videos on your Galaxy S6 device. I will will be glad to assist you with the required information.
Unfortunately, the auto play option is not available on the Samsung devices as of now. I would like to inform you that for the U.S region, all Samsung products are manufactured to the specifications of the service provider for whom they are produced. However, I am taking this as a feedback and forwarding it to our concerned department for a review. Hopefully the auto play features will be added in the next update. Please keep checking the Samsung website to get information about the products releasing from Samsung. "