They are describing a system that can't be hacked by a single individual because there would be a third party with a record of every vote.

The video you cited uses a poorly planned and executed example of an online vote.

The US voting systems are also a poorly planned and executed set of systems.

Electronic voting of any kind is dangerous, it's amazing how much trust is used in any voting but how little can be afford when it's electronic (online or in person machine based).