You don't see it in article 100 because it is defined in their respective articles.I don't see a definition in Article 100.
Those definitions all use the term "raceway" so I don't see how they inform the "tubing vs conduit" debate. What NEC reference do you that rules out the "conduit is a synonym for raceway" interpretation?
Cheers, Wayne
Of course they use the term "raceway" because "Conduit" or "Tubing" is already in their names, they are all raceways.