Before I answer your question I want to make sure we are talking about the same section. You are asking about our five element acupuncture theory page, right?
And on that page right above the mother child points chart you see the following paragraph, "The Mother and Child points for each meridian are derived from the chart above using the following logic. According to the generating cycle the mother of Earth is Fire and the child of Earth is Metal. Using this information for the Yin Earth Meridian (Spleen) the mother point is the Fire point on the Spleen meridian SP 2 and the child point is the Metal point on the Spleen meridian SP 5."
Does that text answer your question?
So Lung (Metal)
The Mother of Metal (Lung) is Earth (Spleen) and the Child of Metal is Water (Kidney) - So the metal mother points is the earth point on the lung meridian LU 9 and the child point is the water point on the lung meridian LU 5
On metal the grandmother is Fire and the grandchild is wood - so no it's not quite the same....