If I knew the answer I would have shared it with you. As you noted correctly, approvals for these ND range is also taking place but at a much slower pace than later 2002 NDs. May be I should not have used the word "blacklist" but for some reason ND's for this range were not FP-ed in time and since they were not FP-ed they have not been approved. After INS acknowledged the FP scheduling problem late last year we saw flood of FP notices earlier this year for May-Dec 2001 NDs. Hopefully these cases will start getting approved too. Rumor has it that these cases were victims of INS's automatic FP scheduler which came on board around mid-2001 in conjunction with the then contractor's screw-up in processing them correctly when they were entered initially. Who knows!
FYI this contractor has since been fired by the INS but for about 3-4 months between April-July, 2001, the INS and the contractor were involved in some legal battles. The result was a complete shut down of receipt notices. For example, I485 application filed in April-May, 2001 time frame had August NDs. Yes, it took over 3-4 months to even receive a notice that your application has been received. So you see applicants around this NDs have gone through a lot of mess.