ARCCA's credibility is important to the reasonable doubt that might exist about JO being hit by a car.
ARCCA answered in the first trial very definitively, in response to the defense counsels questions, that they were not being compensated and that they hadn't discussed or collaborated on the case previously. That turns out to have been a lie.
The were compensated, they did communicate, they did coordinate, and they used an app designed to make that communication untraceable.
When evaluating the reliability and bias of their testimony the jury should know this background.
Edited: If they cannot be trusted to either have understood what they were being asked in the first place, and the truthful answer to that, or they did understand and lied- why should anything else they testify to be trusted.