It requires specialised education to guide free play into a constructive activity. There's a big difference between "Here's a lump of clay. Smash it with your fist until you're bored." and "Here's a lump of clay. Let's try and mold it into something together, like a flower, or a bowl."

Also, depending on the child there can be a lot of learning in the "smash it until you're bored" phase. Then you can show a technique, or help them make something they can be proud of and help, a little, to show they can produce artefacts they are proud of if they seek to learn and apply that learning.

There's also much therapy in smashing clay, it doesn't hurt it as I remind every person I instruct on making pottery.