It was 100% a movie. There were literal surprise witnesses. That's not supposed to happen. It's just a bullshit law and order thing, all evidence known has to be disclosed to the other side, including witnesses. But because it was so viral, people heard about the story, and contacted Depp's team during the trial in order to tell about times Amber Heard lied, including a former TMZ employee and some rando guy who worked at a place called the Trailer Palace. This is an exception, allowed for rebuttal purposes.
There's so much good shit to watch, also. Not just Heard getting eviscerated on the stand. But the TMZ employee basically owning Elaine's soul on the stand, for example:
There's just so much good stuff to watch.