The transform that appears in the entry is the initial transform of each joint, when the actor has not yet had any animations bound to it. This also defines the transform space of the vertices.
When an animation is playing, this initial transform is replaced with the transform that appears in the current frame of the animation. (There are other animation systems in which the animation modifies the initial rest transform. Not so with Panda; here it completely replaces the initial rest transform.)
Thus, if you correctly export a one-frame animation of the initial rest pose, then it will have the following two properties:
(1) The transform defined within each will describe the exact same transform as the one defined in within the corresponding