I don't think that would be a big problem. Hydrogen embrittlement lowers the strength of the material, which I don't think is a major problem with hard drives. They're really never in any load-bearing conditions and you try not to drop them to begin with. A random thought that I had may be that the hydrogen interacts with the various metallic alloys in the platter itself, potentially forming some sort of precipitate that negatively alters the magnetic properties of the platter itself.
