Why do they teach the dolphin kick in swimming lessons for 4 - 5 year olds?

[suebfg]

DS is learning to swim and hasn't yet mastered the basics of front crawl but the teacher is insisting on teaching the dolphin kick.

Why is this? I don't ever remember being taught that in swimming lessons when I was young and I did up to my bronze medal.

I find it bizarre too and they don't tend to cover it for years afterwards. It's too much for kids who can barely keep their heads above the water.

It's easier to learn when younger apparently.