I'd have to disagree with you here. If 450's excelled in this type of riding the hard Enduro series would see more 4 strokes on the podium.
Second, I was switching bikes with a buddy, he rides "a" class hare and hound stuff on a '15 yz 450. The way he had his bike set up made the tight rock stuff much easier than the nearly stock fx.
Like I said the fx wasn't bad, but if that type of riding is what you primarily do, you'll have to spend some time tweaking the fx, and even then there are better tools out there.
Hard enduro is different than the trails we ride. And I'm not a pro hard enduro rider. And I'm not racing. Different horses for different courses.