I do not believe it is a question of doing better but rather facilitating the eventual cranioplasty. If the brain is covered there is less risk for adhesions to the scalp and therefore less risk of injury to the cortex during the dissection for the insertion of the cranioplasty. Also a potential acute benefit of closing some tissue over the brain is the prevention of laceration or strangulation of cortical tissue by the bone edges.

You can use the pericranium, leaving it attached to the temporalis muscle, and sewing it to the dural flap. This way you can dramatically expand the intradural space yet acheive covering for the brain.