I found this on Google Images and the page introduction written by Tigress states an approximate founding date of the Jade Palace training hall, which clearly contradicts the founding date stated on the official website of the first movie. What does it mean?
Not sure what you mean. Oogway is an important character to the franchise, and DreamWorks wanted to make room for some character development while also expanding the story logically. So they changed some of their older stuff to do that.