I think it's a matter of opinion. I don't feed grit to my chicks. When they're about 2 weeks old I start taking them outside (actually my son does) and they peck at the ground. They've always gotten their grit that way. I've never had a problem.
Chick starter is a complete food for them so no, you don't need to give them grit right now. I never could find chick grit at the store, and chicken grit is for birds 8 weeks and older. A lot of people here recommended using clean sand for chick grit and I have done that in addition to their pecking around on the ground during their outside play time. Plus they like to play in the sand!
Oh, wait a couple of weeks, and provide grit once you start introducing treats other than yoghurt or scrambled eggs. Anything that needs "chewing" will need grit for them to digest properly. Whilst they are solely on commercial feed, they don't need grit, because it's formulated as "complete" feed. It digests without the need for grit.
If you give them mealworms as treats (and your entertainment), they will need grit for sure.