I can't speak for your state, but if you care to look it up in your copy Michigan's latest updates you could be sure if it's not there. (if you haven't seen something it doesn't exist?)
I confess that I'm neither Plumber or Pipefitter, just a lowly Toolmaker by trade, but am somewhat familiar with local codes and practices. Depending on job or classification a plumber in our area isn't automatically considered a pipe fitter and vice versa and IMO no one needs to be either to believe that a somewhat brittle metal can suffer from being repeatedly stretched by wedging it outward with considerable leverage.
We're all just 'some guy on the internet' unless we're on the job, and I
apologize for not specifying the obvious reference to GI & BI fittings vs those for high-pressure hydraulics and made of entirely different materials. (I hope no one gets red-tagged for taking perhaps no more than my word for what seems like common sense, rule or no rule.)
Sorry, guys, if I too digressed from the inadvisability of using water or NG pipe fittings (cleared up?) on tractor hydraulics that I a$$umed was relevant to the thread.
btw, Knockrocker, my 'boss' (Master Plumber, Contractor) is ~half my age and recovering from a grand mal seizure last Monday. (His CPK # is finally down from >28k to <5k and he came home from the hospital today.) Why don't I have him run out and open the shop so that I can pore over the code/update books for your personal satisfaction? I'm sure he'd do it for some guy on the internet ...