Panda uses bone-based animation, for the most part. The panda exporter’s job is to record the positions of the bones and put those positions into the egg file. The exporter doesn’t care how the bones got to where they are - IK or not - it only records their positions.
I believe that when using Max, there are a thousand ways to “connect” the mesh to the bones. The only way that works is to use either the Skin or the Physique modifier. Any other method of connecting mesh to bones will not be handled correctly.