Well, that was news to me!!

I have raised chicks for 9 years, and except for chicks raised by their mamas, I have never given them chick grit until I introduced other foods besides chick crumbles to them, usually at 7 or 8 weeks. I have even read that if I want to give them scrambled eggs as a treat prior to that time that they won't require grit to digest it.
So far, these chicks are confined with no access to any foods except for their chick crumbles. But, you made me head out and check it out again. I found the following on the Homestead How To site:
When to Start Giving Grit to Chicks
The need for grit depends largely on the age of your chickens. Chicks do not require grit, so it’s best to avoid giving it to them initially. However, once your chicks eat foods other than crumbles, you can introduce grit into their diet.
Grit should be introduced to chicks usually between 8 and 12 weeks of age. If your chicks only consume crumbles, there’s no need to provide grit.
However, they are a month old now, so I think I will introduce some chick grit to them, based on your advice. I think I will also offer a treat from time to time as well since I know they will have the grit available.