I guarantee this game wasn't built with Unity: 1) Unity bad for building WebGL games. It does multiple conversions to make a WebGL build. Unity offers live editing in its application, but that doesn't apply to web; whereas modern threejs/babylonjs systems offer hot reloads. 2) And Unity is just unpleasant and bloated generally, for the last few years.
Plug for my game[0] if someone wants to see another WebGL experiment (that I devoted 10 years to...better not to ask lol). PS - WebGL supports WebXR, I've been in my world in VR!
0: earth.suncapped.com