It didn't hurt in that particular instance, and that does not mean it couldn't have been turned on him if one of the readers had failed to record (or for any other reason gave ambiguity to his motions) and placed him incorrectly where the crime took place, nor that the practice is inherently good because it exonerated one person. Any more than potentially proving that you weren't at another crime scene makes storing all of your cell phone metadata inherently OK.

Yes, they have this potential benefit, but no, they should not be reviewed solely in that context.