If you don't realize that it starts with an equilateral triangle, it would be very confusing. Seeing as a vast majority of origami is folded from squares, this is a very easy mistake to make.
No one is perfect-everyone has little brain farts where they just don't see something, or see it in a different way-I guess sort of like a generalized, mild dyslexia. Sometimes your mind just doesn't grasp something if it is out of the ordinary. (Sometimes even if it is inside of the ordinary )
Thinking about and independently trying to solve the problem for a while before making a post can usually bypass a brain fart such as mistaking a triangle for a square.
Chin up son, We've all looked so hard we've not seen the obvious!
Remember, simple printed instructions are one of the harder ways to learn a new fold. And though i'm grateful for anyone who has gone to the effort to commit instructions to paper, they can lack some key info.
Have you finished the horse yet? Let's see the pix.
I've folded (or say...'attempted') it quite a number of times but I always end up with something that looks like a grayhound racer . I just can't seem to make it look like the one Brill made.