Your hypothesis is that myopia is primarily caused by the lack of focus on far-field objects.

In a lab environment, wherein there is a lack of focus on far-field objects, myopia does not occur when there is sufficient light intensity. On the other hand, it occurs with insufficient light intensity.

If your hypothesis were correct, then myopia would occur regardless of light intensity, because all of the subjects have a lack of focus on far-field objects. But it doesn't. It only occurs with insufficient light intensity.

That's damning.