Im Just going to give my $19.25
I am a STUDENT

and this is how I see it.
You are a pledge b/c you are pledging your dedication to this fraternity - you become a "new member" when you are initiated. For those who are familiar with BGLO its called "Crossing the burning sands" or "crossing" for short. B/c you are no longer just a regular student, you have crossed over into a new idenity and a new life now.
As a pledge you are not granted any rights - once you are a "new member" you can wear 'naila and do things.
I saw it as a simple distinction, but I could see why others are confused.