Actually... That is not true regarding them starting at #1.
They do skip #6 ever since the first cars were built. But normally the first car numbers to the public are at least #10 and up from there. Now that doesn't mean they haven't produced any below #10 but this is just how it has been over the years.
As for the 30th anniversary cars those are numbered 1-11 skipping #6 to make a total of 10 in each. What I said above is just for the normal production and not special editions.