This was addressed in the post: "Some folks have asked us why we did not fit the Raspberry Pi Compute Module inside. The reason is that above a certain scale,

This was addressed in the post: "Some folks have asked us why we did not fit the Raspberry Pi Compute Module inside. The reason is that above a certain scale, it generally makes more sense to go with a custom PCB rather than a module with a carrier board. With hundreds of thousands of Raspberry Pi 400 units in the first instance, we are above that scale."