Didn't know that. What are the consequences?
I've been doing it for years and they stuff themselves with sunflower seeds.
I haven't noticed any problems. Everybody is healthy and lays like crazy.
Great hatch rates.
They aren't getting the full benefit from nutrients in their feed if the grit isn't appropriate for the size of the bird because it isn't sufficiently ground.
Maybe they are finding sufficient sized coarse stone in their travels.
Sometimes people don't offer grit if they only feed a manufactured feed since the feed is already ground in a hammer mill but grit will still break that feed down further.
I used to take that approach and not provide grit till chicks were outside foraging.
Then on a whim, I gave a batch of chicks a chick feeder of chick grit. (sand size)
They were ravenous for it. I started giving chicks grit from the start. It helps develop the gizzard.
At one point I sold some chicks from a hatch to a friend. It turned out she got several cockerels so I agreed to trade her a pullet for a cockerel.
I had no plans to reintroduce him to the flock so since I was also butchering some of my birds, I butchered him too. I was really surprised at the results. These birds were all from the same flock parentage, same age, same hatch. All of my birds' gizzards were twice the size of that of her bird she had raised from a new chick with no grit.
They don't have teeth. The grit in the gizzard serves as their teeth grinding the feed after it leaves the proventriculus (first stomach) where digestive enzymes mix with the feed. If we swallowed without chewing our food, we would get the same result that chickens do without grit.