When having gltf and glb file georeferenced, the coordinate could be very large, for example here in Beijing, China, a typical coordinate under epsg:3857 would be something like:
I think the Cesium rendering engine stores positions using 2 float, to effectively emulate 64 bit precision, which is why it’s possible to place things at these very large coordinates.
The other thing was, at least with glTF 1.0, Cesium had an extension to store the world coordinate separately, and all the model vertices would be relative to that origin so they can remain small: