The weird behavior of the rotation animation of the attached model.

The behavior of the attached model can not be explained.
The model can be displayed correctly in Windows 10 and online gltf viewer (https://gltf-viewer.donmccurdy.com/). But I find the 481 quaternions which are used to define rotation animation does not point to the same direction (see the following data I calculate by programs and by online calculator). You see the axes change over time, but the rotation animation shown in windows 10 and online viewer point to the same direction. The rotation animation does not reflect the changing axes. Would you please explain the reason?
[willy.zip](https://github.com/KhronosGroup/glTF/files/4210933/willy.zip)

- Quaternion {0.104911, 0.051215, 0.963975, -0.239003} rotation: angle=207.655 axis= Vector 3D {0.108042, 0.0527436, 0.992746}
- Quaternion {0.10523, 0.0524935, 0.963906, -0.238867} rotation: angle=207.639 axis= Vector 3D {0.108367, 0.0540584, 0.992641}
- Quaternion {0.109073, 0.068175, 0.96294, -0.237069} rotation: angle=207.427 axis= Vector 3D {0.112274, 0.0701755, 0.991196}
- Quaternion {0.111025, 0.0759884, 0.962338, -0.236229} rotation: angle=207.328 axis= Vector 3D {0.114259, 0.0782017, 0.990368}
- Quaternion {0.115788, 0.0959159, 0.960612, -0.233703} rotation: angle=207.03 axis= Vector 3D {0.119086, 0.0986476, 0.987971}
- Quaternion {0.120694, 0.115701, 0.958375, -0.231438} rotation: angle=206.764 axis= Vector 3D {0.124062, 0.11893, 0.985121}
- Quaternion {0.124988, 0.134451, 0.956027, -0.22872} rotation: angle=206.443 axis= Vector 3D {0.128391, 0.138112, 0.982059}
- Quaternion {0.134006, 0.171482, 0.949981, -0.223993} rotation: angle=205.887 axis= Vector 3D {0.1375, 0.175953, 0.974749}
- Quaternion {0.136577, 0.183496, 0.947845, -0.221959} rotation: angle=205.648 axis= Vector 3D {0.140071, 0.18819, 0.972093}
- Quaternion {0.150457, 0.242374, 0.934411, -0.213291} rotation: angle=204.631 axis= Vector 3D {0.154001, 0.248083, 0.956419}
- Quaternion {0.16584, 0.312769, 0.913438, -0.200757} rotation: angle=203.162 axis= Vector 3D {0.169286, 0.319269, 0.932421}
- Quaternion {0.169244, 0.326407, 0.908475, -0.198713} rotation: angle=202.923 axis= Vector 3D {0.172688, 0.333049, 0.926961}
- Quaternion {0.181911, 0.389975, 0.883463, -0.18526} rotation: angle=201.353 axis= Vector 3D {0.185115, 0.396845, 0.899026}
- Quaternion {0.189268, 0.420449, 0.86896, -0.179745} rotation: angle=200.71 axis= Vector 3D {0.192402, 0.42741, 0.883347}
- Quaternion {0.198108, 0.471629, 0.842889, -0.166906} rotation: angle=199.216 axis= Vector 3D {0.200926, 0.478339, 0.854881}
- Quaternion {0.209198, 0.520271, 0.813134, -0.156099} rotation: angle=197.961 axis= Vector 3D {0.211794, 0.526728, 0.823226}
- Quaternion {0.21396, 0.555092, 0.790459, -0.145833} rotation: angle=196.771 axis= Vector 3D {0.216272, 0.56109, 0.799001}
- Quaternion {0.227581, 0.620786, 0.739252, -0.127818} rotation: angle=194.687 axis= Vector 3D {0.229463, 0.62592, 0.745366}
- Quaternion {0.229094, 0.637685, 0.725252, -0.121997} rotation: angle=194.015 axis= Vector 3D {0.230818, 0.642484, 0.73071}
- Quaternion {0.242991, 0.71651, 0.646902, -0.0953213} rotation: angle=190.94 axis= Vector 3D {0.244103, 0.719787, 0.649861}
- Quaternion {0.251179, 0.789065, 0.55683, -0.0650151} rotation: angle=187.455 axis= Vector 3D {0.251712, 0.790738, 0.558011}

Start by inspecting the attached willy.zip model and its 481 rotation-animation quaternions, then compare the result with the Windows 10 display and the linked online glTF viewer. Done means explaining why the changing quaternion axes produce an animation that appears to point in the same direction, or identifying a reproducible specification or implementation issue.

Written by the indexing model from the issue text.