Don't forget that in the meantime, Apple had three other power adapters. There was the 100-series simplicity, the 500-series monstrosity, and the 5300-series tragedy. Then they went and re-used the Duo on the 1400 on up through the G3 and clamshell iBooks.
But, Apple then got a bug up their behind and decided to make what looks nearly identical, but is slightly differently sized. Why they did that completely escapes me.