OK, Rick, I think your comments have helped me crystallize my thoughts.
These are the 3 theories (the 3rd is your idea):
1. eBay choked selectively: dealt with my AS snipe correctly, but choked on the other bidder's single snipe service (which placed 5 identical bids at identical times). [Possible, but unlikely.]
2. eBay did not choke. The other bidder used a single sniping service, and that service had 5 servers place identical bids, but those 5 servers were not synchronized. [Possible, but unlikely.]
3. The other bidder used multiple sniping services/programs. This certainly could explain the lack of synchronization but as you point out it would be major overkill, at least for this particular item. Though I can imagine someone setting this up as their sniping system in general, regardless of any one item, on the belief that this makes it more foolproof than any single but reliable sniping service (effectively false, but a comforting belief). [Possible, not so likely.]
Of these 3 theories, I am inclined to believe the 3rd.
Thanks again for your input, Rick.