i don't think its about the highly strungness or otherwise, for me it's about a lightness of touch, the stuff that makes the hair on your neck prickle, or puts the tear in your eye - IW's performances are often flawless, they just aren't *magical* to me.
My glasses maybe need reconfigured because I've really enjoyed IW/BR's tests that I've seen.
I don't see a "dull" or switched off horse. I think BR had a more open and pleasing (to me) frame than any of the others today. BR perhaps looks more comfortable/content than other more highly strung horses?
I'm with you here TPO, I dont see anything remotely dull, mechanical or switched off either. I see an ability to produce huge athleticism without huge tension, and a remarkable partnership and trust with her rider.