If I were subpoenaed, I would just go there, and answer questions.
The fact that they are making prepared statements is like advocacy...like they've got a dog in the hunt. "Here is what I want to say..." Who cares what you want to say?...other than to hear your biases.
Today, Sondland said there was QPQ in his statement...then under cross, he said there was no QPQ evidence other than his presumption, and admitted he was specifically instructed that there was no QPQ. Very weird...totally undermines his effectiveness as a witness. But, I guess the Left got what it wanted, because people like Frank and scooter and 521 still believe his 23 page operning statement, and just disregard the cross-examination that exposes the falsehood.