First, keep in mind that this is a modification to hard drives and not DVD-like equipment. The heat pulses in the case of the article are still modifying the ma

First, keep in mind that this is a modification to hard drives and not DVD-like equipment. The heat pulses in the case of the article are still modifying the magnetic bits on a spinning metal disk. Second, it seems that it's faster to generate these heat pulses than it is to switch the magnetic orientation of the write head. I haven't looked into the physics, but this is the only plausible explanation my limited imagination can fathom.