I don't see how you can doubt the artistry of this.
As for outdoor use, I can easily see why that would be rejected (apart from the fact this is a piece done especially for an exhibition, and was obviously designed for the space).
First there is practicality. Guitars aren't waterproof. Amps aren't waterproof. Power would have to be supplied. A generator would interfere with the sound. The area would have to be fenced off to avoid vandalism (not to mention possible electrocution). It would have to be curated, and finally birds in a natural environment would probably spend more time in trees.
Second there is purity of concept. How would you integrate this piece into the natural evironment? How would it change?
The use of a domesticated bird species cannot be accidental. This is a installation, designed to be experienced in a space, in a gallery. That creates a certain fabric of expectations and so forth. Using domestic birds in a caged environment evokes the concept of imprisonment, of music as spectacle, romantic ideas of the singing bird in the cage, rockstars as painted sogbirds, etc. Al so the gallery space provides the artist with total aesthetic control. In many ways designing conceptual art can be like scientific experiments. You've got to control the variables. If you're already incorporating one aleatoric element you don't want to incorporate too many more, or the work becomes muddled. You have to remember that the audiences subjective experience is also largely out of your control, though clever use of context can help here. When you place works, especially kinetic works, outside, unless they are engineered on a monumental scale, or with monumetal materials, the work almost inevitably picks up a suggestion of dealing with entropy and decay that you may not want to tackle.
The video is only a brochure or advert remember, not the work itself. Installations rarely translate well into other media.