Can you use Threaded Fittings on pipes larger than 2 in.?

NFPA 13 2019 says "16.8.4.1 Screwed unions shall not be used on pipe larger than 2 in. (50 mm)." But I'm not sure if that includes threaded fittings, or if screwed fittings are different from threaded fittings. I ask this because a company attempts to install a fully threaded 6in riser for a sprinkler system and we want to warn them that's not a good practice in order for them to make it grooved.