Yes, these cecals are the most evil aspect of chickens. They exist expressly to gross us out, offend our sense of smell, and drive us crazy trying to clean them up before they permanently stain our walkways.
But it's a normal part of chickens and that cecal is within normal range. If it was a watery puddle of black gravy with yellowish ribbons of mucous in it, then you might be seeing a sign of bacterial infection.
Cecal poop ranges in color from dark chocolate to rust/tan color, all smelling like something the devil left behind. But for a chicken, it's just normal poop.