API method LoginEX

Quick question about LoginEx2  or  LoginEx API method. The documentation says the following, but I am interested in the last option.

Authenticates a registered user. Accepts a promotion code. Allows three options for authenticating: Username and password, email and password, customer number and phone number and zip code with optional email address for further validation.

I am trying to understand  why when I use the customer number, phone number and zip code with optional email  to login. Why is it making me log into TNEW again to checkout if I have already been authenticated?

Thanks,

Travis

 



[edited by: Travis Armbuster at 11:13 AM (GMT -6) on 27 Nov 2013]