I just chatted with Samsung live chat thing. They said it is a feature
"Alastair: Hi, thank you for contacting Samsung Technical Support. How may I help you today?
Visitor: Hi, can you explain to me how to get my Galaxy S5 to wake up while the screen is off using S voice?
Alastair: I understand that you require information how to wake up the device using S Voice. Is that correct?
Alastair: Thank you for confirming.
Alastair: May I know the model number of the device? You may find it in Applications>Settings>General>About Device. You can also find the model number beneath the Phone's battery. Generally model number starts with SGH,SPH,SCH,GT or SM.
Alastair: Thank you for the model number.
Alastair: I would like to inform you that you need to say "Hello Galaxy" to wake up the device.
Visitor: can i do this while the screen is off?
Alastair: Yes, the device will wake up when the screen is off."
After a long chat, and factory resetting, they recommended me to return it to Verizon. Still cant get it to work
Guess I will wait and see if this problem is addressed by Samsung, or if the Samsung live chat person has no idea what they are talking about.