I grew up when antibiotics were a thing, and it was well known that puncture wounds from something like a nail needed immediate treatment because of risk of tetanus. Wounds from an animal also needed treatment because of the potential for rabies.
I think it's relevant that this is a UK story. No one would think of the potential for rabies here as it was eradicated before most were born. Unless you're handling bats, which you shouldn't be doing as a rule.
Which is funny because nails, or anything metal really, have nothing to do with tetanus, not more than wood, glass, plastic, &c.
It isn't that iron is pathogenic, but that nails inflict deep wounds, and inject many pathogens from the environment. Needle/cutlery punctures, for example, are not associated with tethanus because they aren't rusty or in close contact with decaying matter.