They do ship on Saturday...my S7 edge and lot others S7 pre order was charged, shipped on saturday Feb 27th for delivery on Feb 29 Monday.
Not directed at you but before anyone jumps...that's S7 edge different phone, month etc. That's true I can only say based on what I have seen happen in the past pre orders.
UPS doesn't ship on Saturday, but they might have something special for the carriers for this.
Like I said, I have a feeling that UPS and FedEx have had the phones at their hubs and they are doing the processing.
I wouldn't be shocked if they had a special deal for carriers for shipping on Saturday and Monday delivery when phones are released.
It just isn't the norm for UPS. Even if I drop a package off at the UPS store on Saturday (hubs aren't open here on Saturday) it won't ship until Monday. A special deal for shipping out phones at release with all the carriers, that I could see.