I think because they wanted to let the air out gradually so they could inspect the tire afterwards, they weren't interested in tearing a big hole in it from a h

I think because they wanted to let the air out gradually so they could inspect the tire afterwards, they weren't interested in tearing a big hole in it from a high velocity projectile. They even started with a hollow drill bit, but decided that wasn't needed. They used the camera on the tank to pre-inspect the tire before deflating it, which would have given them close ups and angles of view that wouldn't be possible with just a distant telephoto lens. And for only $3000, it was probably much cheaper to build this than to put in place all the range safety procedures they would have needed to shoot it.