I can confirm, that the Spline IK Baking is broken.
I had a fairly long chain ofbones (~30) and when baking the animation, the tip of the cian was just everso slightly off to not match with other animations.
I managed to solve it in the end by creating a second chain of bones, then clearing all the parents, and then constraining the with a "copy transform ocnstriant" to the corresponding bone in the spline ik chain.
Its an ugly hack, but it works.