Buttons are a trained behavior. It takes training to get a dog to use those buttons and most credentialed trainers will heavily rely on rewards for training. The researchers here were trying to use an innate behavior. That makes sense because they want to check if the dog would use an innate behavior to initiate communication. If they rely on a trained behavior the dog may be doing it to get the reward that was used to train the dog and NOT doing it solely to initiate communication.

A lot of those talking buttons videos you see in my opinion are either scripted/edited or a bit of projection/reinterpretation of what’s going on in human terms. I have a dog I love to death and the lengths people including myself will go to reinterpret their behavior in human terms is incredible.