So do some manufacturer's just design their hardware "their way" and assume that you won't need access to address 512? Maybe its a design flaw. I have seen other dip switch tables that use switch 1 on to = address 1 and only 9 switches. Others use the switch sums +1 approach.
Another perplexing thing about this is my Boss has an iPhone DMX switch setup app. It shows 9 switches. When you enter 512 in it, it shows only switch 256 on - all others off!? And when 256 is entered the same. When 511 is entered all switches are on.