This dimension is recommended because the plating on the holes has to be done properly. This is the minimum required dimension. However, it is better if it is more than a 0.15 mm(6mil) gap for via holes.
An Annular Ring Width = (diameter of the pad - diameter of the hole) / 2
The quality of the plating on the holes will be better if the via holes dimension is 0.4 mm.
The image below shows the exact dimension of the via hole and the annular ring,