I just think you hear about it a lot because it's common for Poicephalus to be kind of "hair trigger" like that. Every single person I've heard of who has or has had a mature Senegal will tell you the same thing.
I don't have a Senegal, but from my observations over the years, and speaking to owners of the other similarly sized Pois - Sennies, Red Bellied's, Meyer's, Brown Headeds, and from my personal experience with a Red Bellied and a Ruppell's, it seems like they all have this particular trait in common.
Robin (Red Bellied) was a typical one person bird for many years, and many people I have known dared to pick him up to say hi to him, and had to sustain a deep and painful bite from Robin where many times he had to be pried off the unfortunate person's flesh. When Robin was in his teens he met Don, and it was instant love. I would warn him, I would go find bandages, but was shocked to see we never needed them! Maybe a few times in several years Robin bit him, but any Poi owner could expect that. He is now a two person bird after many years.
Griffin the Ruppell's is a typical one person Poi. We tried to socialize him young, from 4 months old, but he was already pretty set in his opinion by then!
Sennie Tude as Mark (Birdman666) calls it. All Pois have Sennietude lol!