This two-list situation has confused many pax for a long time. I've never seen it written in any customer material - the only way I know to find out about it is experience ... or I guess reading FlyerTalk.

Here's a link to a thread from a while back - scroll down to my post in it, I go through all the hoops re the two lists.

http://www.flyertalk.com/forum/Forum21/HTML/009510.html

Lex made an interesting point in this thread - that perhaps asking people to sign up twice gives upgrades to those who really want them. I was starting to agree with this... but your experience clearly shows what can go wrong...