Can an effective plan be reversed if buyers back out?

From the NYT article on the Linden 78 The developers were required to close on at least one unit by April 1. One buyer did close on a $3 million purchase on March 31, but the closing was not counted by the state attorney general’s office, since the building did not yet have a temporary certificate of occupancy. Those buyers too may chose to withdraw. The condominium plan has now been declared effective, but the approval could be withdrawn if too many buyers back out, brokers said. My understanding was that once AG declares plan effective, this can't be reversed even if buyers back out and taking them back below the 15% requirement?