Again, the point of the video is how one R+ trainer dealt with a problem behavior. From her blog (which was linked in the video description):
Having three girls in heat in the house can be a challenge with three intact males. This is the first time that I have noticed that Epic really found girls interesting, and a new world seemed to open for him. Instead of trying to survive these days, we’re making the most out of this high value reward. Bitches in heat will be allowed in Swedish agility trials from this year, so it’s good to be prepared.
It's really great that you guys have dogs that are able to work next to a bitch in heat without going crazy. Apparently this trainer wasn't so "lucky" with her dog, and some training was required. Certainly there are things that distract your dogs, and you've had to use one method or another to teach the dog to leave it and work through it.
This trainer employed a method of "if you do what I want, you might get what you want." This is no different than rewarding with treats, ball, praise, etc. In fact- as the text in the video directly states, value was built for the nose target because a higher than normal reward was paired with the activity.
Regardless of how you feel about using a bitch in season as a reward, this is simple psychology. Pair a higher reward with a behavior, and the behavior will be more likely reproduced. This is the Premake Principle in action.
(And it doesn't really matter if you can't see the dog is performing the work more enthusiastically or not- I promise that the world-level trainer is quite aware of if her dog is more enthusiastically performing or not. I doubt she's just lucky enough to happen
to get to that level of competition without such skill.)