Is it useless to have a hot, warm, and cold nodes running on the same server?

Like the title suggests. I saw that in the ILM policy, it says that it's recommended to move the data to warm nodes.

So I made a Docker container dedicated to a warm node to move my data into, but the hot data and the warm data are on the same server. So is that setup useless?

Kindly share a reference related to this, because I haven't found anything exactly related to this.

Thank you.