So they say. That would be a disaster.
They have to have a backup in case the traveller for some reason cannot present the QR-code. Be it lack of ability, internet, or power on the mobile.
It can happen to everyone; I went to Malaysia shortly after they introduced their version. I filled the form and loaded the email on the phone so it was ready to present at arrival. However, when unlocking the phone, it tried to access the internet and wouldn't show the email when there were no internet. Thus, I had to use their backup system - a guy filling the form for me on his phone. No free internet at arrival back then. I plan to bring a printed QR code when arriving in Thailand next time.