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Interesting in that when it comes to computers, he [Rob Pike] knows what he's doing.

Clearly not. For one thing you just don't erase a working drive with your data on it until the repair is successful. If it's some warranty thing and they are going to take the drive then you at least make a 1:1 image of it using dd or equivalent block copy first. If they are replacing it with the same size just dd the image back for that matter.

The worst part is this repair is trivial for anybody that knows what he's doing. You just order a replacement drive from newegg (or wherever), mount the new and old drives using target disk mode or external enclosure, and copy the disk. Then you swap the drives. This wasn't an Air or something difficult, just unscrew the case and replace the drive. Or if you really don't want to take it apart yourself have the repairman do the swap.

It's really easy, especially with a second Apple available. I did it just a few weeks ago for a family member, the only actual time investment is opening the case to swap the drives.