Because there are so many different cultures on Borg, Cero couldn't be properly prepared no matter how much he learned about them.
He knew that the civilization, the people that dominated Borg, were commonly referred to as Reptilians, and he knew that there were many types of Reptilians.
The Reptilian on his screen, caged, imprisoned, and previously chosen as a sacrifice, was part of the lower castes of Reptilians.
The lower castes were deemed inferior due to their different physical constitution. Many of them had scales, long reptilian tongues, etc… But they usually had, one way or another, less reptile-like features.
The imprisoned one being broadcast in particular did not have a reptile's skull shape.
Cero also knew about a different Species of Borg. A Species that lived in the wilderness, and that he aimed to devour plenty of to clear his Quest and obtain Regeneration Lv.MAX
The Kurnish.
