We may finally know what caused the biggest cosmic explosion ever seen

Is this trying to say that the stream exiting a collapsing black hole emitted at nearly light speed contains matter and anti-matter that collide to create an even larger release of energy in the form of gamma ray bursts?

Scientific article 'A bright megaelectronvolt emission line in γ-ray burst GRB 221009A' on ArXiv: https://arxiv.org/abs/2303.16223