Yeah I have seen it, and he does say that, but I still say Frieza has 4 forms.
The first form (the little form he's in with his armor and female-like voice) is form 1.
It does count as a form. Why? Well touch your arm...right now. It has form doesn't it? The form you have as a human (or whatever you may be) is a form, is it not?
And if you were to some how change your physical appearance, this would be your second form.