I agree it changes the animation effect for everything on that named layer.

You can then select another item to change the animation on that without having to re-display the dialog provided you select another layer.
might be a better wording. But like so much with Xara it's just kicked into the long grass and left unfixed.

The one that really gets my goat is drop a new colour on the page rectangle and Xara reapplies a drop-shadow to the page. How many years have we moaned about that!