Use timeline's frames or use mc's own timeline?

on various sites like this one: http://www.no-tec.com/not_quite_there.html, he probably used the original timeline for motion tween and so forth.

But for me, after the preloader, when i do stuff, what i do is i dont use the orig. timeline but i use mc’s own timeline to create animation.

Is this a bad way to create animation at the start?