Here's how it's supposed to work: Whenever any field value in the form changes, the calculation scripts of all fields that have them are triggered, in the order defined by the field calculation order. I haven't read through all of that or tested your samples yet, but I'll let you know if I have anything to add.
I just looked at the samples and have a few comments:
1. For the first sample, you said you selected "Commit selected value immediately", but the fields aren't set up that way.
2. With Acrobat 9 on a Macbook, it worked as expected using both the keyboard and touchpad.
So everything is normal for me. I'll see if I can test with some other combinations of Acrobat/Reader and OS later.
1. I updated the PDF; you can try the link again.
It appears as if the calcualtion events are triggered for all the fields when I select an item in any field now -- keyboard or touchpad. It was just probably me. Sorry for the confusion I caused.