Are grommets (Arlington SB130) required when running ENT thru metal studs. I've read Article 362 which doesn't address it, and article 300.4 (B) (1) which only mentions Romex needing the grommets. So I guess they aren't required?
Nope, no requirement to use them. If you ever have an issue with steel stud edges sawing through your EMT, you've probably got bigger issues on your hands.
Crap, I just noticed that you wrote ENT, and I addressed EMT. I don't use ENT much, but I do pop in a grommet here and there to make pulling the piece in easier. I use the stuff on the rolls, and not the sticks.