I'm also a beginner, but my understanding is that there are various ways to play any given chord, and that what makes the most sense in any given situation depends on various factors (what chord came before, what chord comes after, personal preference, etc. So yeah, they teach one way of forming a chord and have you practice the hell out of it, 'cause that's how learning works, and then they have you modify what you're doing, 'cause that's how playing guitar works. Frustrating, but it's the nature of the beast.