It might be the unique plot. Maybe it takes the RWBY characters and puts them in situations that are different from the original series but still in - line with the overall RWBY universe.
I'm not sure of specific fanfics similar to it off the top of my head. But you could try searching on RWBY - dedicated fanfic websites like Archive of Our Own. There are likely to be fanfics with similar themes or tones.
There's no way to really tell if it's common specifically for someone named Jojo. However, in general, reading fanfiction is a popular activity among fans of many different franchises. The Jojo series has a large and dedicated fan base, so it's likely that there are fans named Jojo who partake in reading fanfiction, but we can't say for sure how common it is without more data.
Perhaps this Jojo is interested in exploring different interpretations and stories within the Jojo universe that fans have come up with. Fanfiction often takes the existing characters, settings, etc. from the original Jojo series and creates new and unique storylines. So, this Jojo might be a big fan of the series and wants to see what other fans have imagined.
A'man bites dog' story refers to a concept where the unexpected occurs. The phrase has become a sort of shorthand in media and communication. It implies that the typical or expected order of things has been reversed. We are used to hearing about dogs being aggressive towards humans, but when a man bites a dog, it's so strange that it stands out. It's like a disruption of the normal state of affairs, and such stories often get more attention precisely because they are so different from what we usually encounter.
There was a woman who found a spider in her bed. She didn't think much of it at first and tried to shoo it away. But it bit her on her hand. The bite was from a black widow spider. Immediately, she felt a sharp pain. Her hand became numb, and then she started having muscle cramps all over her body. She was rushed to the hospital in a lot of pain and fearing for her life.
I'm not certain, but it could potentially mean a short story that is related to 8 bites. Maybe it's about a character who takes 8 bites of something during the story, like 8 bites of an apple that leads to a series of events.