That's right. In the case of OG Kal, S2 is better for handling lots of trash mobs since it hits all blocked targets, while s3 is better for killing single tanky enemies since it's single target true damage. In IS, her S2 can also be used as a healing skill, while the S3 is more selfish
Most operators have one skill that's better than the others, some have a second skill that's as good as the first or at least is decent in different situations, and it's very rare to have an operator with three strong skills that are all equally useful