in fact transform axis is different according files, and import parameters (left handed, flipwinding order)... because it's a post transformation of bones and it depends of its original matrices...
Blender export inverse y and z and polarity, it's why axis where inversed in wz. But in most of other files y and z are common to wz4, axis are in good order.
I swith back y/z axis it's more natural for most of files.
For blender maybe there is an option to switch axis at export ?

I've tested you boxer model. Transforms also differ from wz4's original ones. But anyway... It's not that important...
In Blender's collada exporter there's only this choice: Matrix/SRT/Both. By default it's set to Matrix. I'll see it works.

I've tested you boxer model. Transforms also differ from wz4's original ones.

yes, y and z axis polarity is inversed. but not axis.

All that really depends of axis system of the original modeling tools and it exporter. (boxer comes from daz studio).
Can't do something really generic here so I leave it in the same wz natural axis. It's not really annoying as naturally find the good axis parameters when you use it.

OK. Let it be like this.

Ikam, there is a bug when I try use assimp animation object + SSAO. Can you fix this?

It's because some clusters are not assigned with a material (the previous example file is bad), it result bad shadows.
To fix that, just after importing mesh, put a setmaterial with a default material (skin for example) and choose "all clusters" mode (it will ensure that all clusters have a material).

Tanx, Ikam, l'll try this!☺