It'll work - for an unknown period of time - until the bar snaps in two while you're riding.

It's always a bad idea to remove material from the wall of thin tubes (all tubes are thin-walled). Sanding the center section of a handlebar strikes me as a VERY BAD IDEA. I doubt many people have ever done this, or at least would admit it. Looking for a handlebar and a hospital out in the boonies is never a fun time.