[AZ-AlphaXi]

Ok here's what the NPC "green book" says about snap bidding
under the rush mechanics section:

Snap Bidding
Snap Bidding is an option available to chapters which did not fill formal membership recruitment Quota spaces in bid matching, whether matching by hand or by computer. Snap Bidding is not intended to fill spaces in the chapter Total. Snap Bidding is limited to any woman who participated in the designated formal membership recruitment.

Snap bidding should be under the direction of the college panhellenic membership recruitment committee, working with the chapters who have quota vacancies. A signed membership recruitment acceptance shall be filed with the college panhellenic before a woman who has accepted a snap bid may be pledged. Snap bidding shall begin immediately after bid matching and end with the distribution of bids, at which time Continuous Open Bidding shal begin

end quote

Nothing is said about requiring a PNM to have completed the recruitment process (ie to have attended preference parties or signed a preference card). In fact there isn't anything said at all about how snap bidding is supposed to function. So my guess is that any snap bidding rules are acceptable to NPC as long as the basic tenents of 1) having participated in some portion of recruitment and 2) that mutual selection (ie both PNM and sorority must agree) is perserved.