Change the shapes slightly and they can still be fitted together to make any size sweater you want, without having to make a tension (gauge) square.
These two sweaters are the same basic design. The first set of shapes around the neck is exactly the same in both. The next shapes have been amalgamated in the dark version, to make them look different.
The dark version was made to use up yarn left from another sweater so there is a large plain area at the bottom, with stripes, to use up the last remaining bits of purple.