M chips are super expensive. They’re optimized for low clockspeed/idle efficiency and pay through the nose for cutting edge processes, whereas most gaming hardware is optimized for pure speed/$, with the smallest die area and cheapest memory possible, at the expense of power efficiency.

And honestly the CPU/GPU divide over traces is more economical. “Unified memory” programming isn’t strictly needed for games at the moment.

And, practically, Apple demands very high margins. I just can’t see them pricing a console aggressively.