Because the game does not offer a full-room VR experience, players use a joystick to push their character forward. This can create the sensation that your body is moving forward, without actually going anywhere.
Because each person's sensitivity to balance and motion is different than the next, people naturally react to VR differently. Motion sickness is a common side effect from being in VR too long, but usually is something that the average person can get used to with practice.
With that said, as someone who is not at all new to VR games and who has personally never experienced this side effect before, the disorientation became so bad it prevented me from fully enjoying the game.
More than once, that sensation caused me to lurch forward in the real world, or briefly lose my balance while standing with both feet planted on the floor.
After a solid 30 minutes of play, I really wished I had chosen to play in a chair. By the end of the session, I left the demonstration feeling nauseous.