While I agree the "Baboons" and "Alligator" could very easily be mistaken versions of the Mandrill and Saltwater Crocodile. I still can't really understand confusing the very specifically labeled "Dik Dik". The only animal that is sorta close is maybe a baby Springbok, but they are very distinctly different. Most people are unaware what a Dik Dik even is so to mention it by name just seems odd if it was just a generic gazelle. The other thing that threw me for a loop was the description of the "Baboons" enclosure. A "Dusty sand pit" wouldn't describe the needs of a Mandrill (which needs a lot of foliage and climbing structures, needing a lot of soil if anything) or a Japanese Macaque which needs snow. A sand pit would actually be a good descriptor for an actual Baboon, especially a Hamadryas baboon that lives in the desert.
At this point there is a lot of evidence to kinda say that decorations in the game indicating other species were just lazy research on part of whoever developed said pieces. If I am a 3D artist at Frontier and they tell me "Make a camel and a rhino sign" I'm just going to make signs for the first camel and rhino I see. The signs in the game show many errors. The camel sign is a Dromedary, even though we only got the Bactrian. The Rhino sign is a Black Rhino, even though we only got the Indian Rhino. The seemingly crocodile sign was labeled "Alligator", but similarly the Asian elephant sign is labeled "African Elephant".
If I had to guess, some animals that were initially planned were simply scrapped for DLC. There is too much evidence for certain animals to not exist. So while I'm "leaning" towards the article merely misidentifying animals, I could also just as easily see them playing an earlier build of the game with what were later found to be scrapped animals.