hmmm...
He has a 20 GB drive with two platters for a 75GXP family. So, only three heads are being used. The platter with the scratch was done while the product was open by IBM or Manaz. If you take a drive with the head stack unparked, you can't shake the drive hard enough to get them to move. Even when you move the head stack with your fingers, the heads don't leave a noticeable mark. When you throw a drive and let it hit the ground, it still won't scratch the platters in that manner; usually just divots are created (I’ve sent plenty of drives through the ringer). Since Manaz insists that it wasn't him, I'm expecting the scratch is the fault of IBM. This would explain why a two platter, 4 head (from what I could see there are four heads, although the pictures aren't the clearest) drive is formatted to 20 GB. The scratch mistakenly passed quality inspection and once the drive was closed, they had a problem with that platter side, so they turned the head off. (It is much cheaper to turn off that head once the drive is closed then sending it back through the assembly line.)
This scratch, however, does not directly present itself as the culprit to the drive failing. It does tell us about some quality issues that IBM had during assembly, which could be the cause of IBM’s mass failure.