Nothing stops you from running the app nonstop and mounting the phone on the wall. In Android, this is called Kiosk mode. It prevents any other apps from running on the phone.
Have you seen the size of that thing? that's 48x18cm, or 20" diagonal. That's not even close to the phones.
And yes, thing thing _could_ have been implemented as a embedded large-format Android tablet with the kiosk mode app, installed in a wall-mount case. This would likely be more expensive to produce, and would look worse.
In other words yes, you can cut paper with knife.