It's not about belief. It's about how the political spectrum used to be taught. Hence the word, "traditional". These terms have evolved over time.
How odd. When I went through, it was taught exactly how it should be. By a proclaimed liberal teacher, no less.
My sister has also seen the same thing. She has been taught the same way.
The problem is the other teachers who interchangeably use the word "Fascism" for "Reactionism," thus causing people to believe that Fascism is a right wing enterprise. Never once did I have a history or government teacher / professor ever use the word wrongly.
However, every other liberal I've come across has used it wrong.