They cannot naturally run real Minecraft on their CPU. Instead, they have handcoded Minecraft like game for their custom CPU, so the title is a bit misleading. For this CPU/language you will find an emulator.
It's definitely a little misleading, but idea of running the entire JVM with graphics stack included is so insane that I'm willing to call this "minecraft in minecraft"
You can find more information in the explainer video https://youtu.be/xIMkqHb2-KM