It was probably purchased in 2006. I have seen descriptions that conflicted with the summary. It was obvious that the seller bought NOS that was older than advertised. I think it is a case of just not knowing any better.
Heck, I even saw a guy advertising a Waterford as new per the summary and then stated in the description that he had sent it back to Waterford for repaint. You don't send a new bike back for repaint. I called him on it and he referenced his record of hundreds of E-bay sale versus my couple of dozen. I replied back that it did not take any E-bay transactions to determine the bike was not new. He finally said he would change it just for me!
I am very careful on E-bay. But there are some good deals to be had. As long as there are not significant differences between a 2005 & 2006, the bike is in good condition, and you got a good price I would not complain.