Rhythman,
It was a part of her routine clinical exam for me for the purpose of observing progress (or lack thereof) Its along the lines of checking soft palate elevation, strength of jaw closure, stick out the tongue, wiggle it, smile for me, etc. At this point I'd already had an EMG positive for MND.
P.S. I'd had no problem whistling for previous exams. I think I was being seen about every two months back then.... Now, before we get a lot of nervous people who can't whistle being afraid they have bulbar onset, please remember that many people cannot whistle, its somewhat like a talent, not exactly, but its not everyone's God given right that they will be whistlers. By itself it is not remarkable. In my case it was significant because I could whistle well before.