Don't know. My smallest DS is only learning to write and I found that although he held his pencil correctly, he was pressing a little too hard, thus making writing more difficult. I purchased an ergonomic pencil thing with grooves for the fingers to sit and it has helped with pressure and his writing is marginally better.
My eldest DS... well, his writing was awful! I also invested in said pencil and it didn't help a jot. He does write with his wrist bent at a funny angle though so that probably doesn't help.