Reading this I wondered ? I assumed it was only about really large weapons.
Routh has a criminal record dating back to at least 2002, when he was convicted in Guilford County, North Carolina, on one felony count of possession of a weapon of mass destruction, according to a review of state court records.
That was the traditional meaning of the word, yes. However it has been horribly misused to push headlines and in the legal arena it has been used to push for harder penalties on what would be considered traditional weapons.
It’s a pet peve of mine because it dilutes the word, but home made preasure cooker bombs have been called WMDs in the US and people seem OK with it.