As I understand it, the Eticket thing isn't a park admission ticket. It's just something to keep you in the park longer. You have to use a hopper ticket to get into the park, then once in you can trade it in for the arm band to stay later.
The E-ride Night ticket must be used in conjunction with a multi-day admission pass. It doesn't give you access to the park, it only keeps you from getting kicked out (for a little while, anyway.)