There is also a train of thought that by getting something hard into the gizzard early you start to build it's strength earlier. Long as they are on commercial processed feed they are fine with or without, do what works for you.
What I try and do when I see conflicting opinions is consider what the chicks would have in the barnyard if they had been a natural broody hatch. They would have access to sand and pebbles and be eating anything they found. Granted with commercially produced grower feed the grain is milled enough to not "need" grit, but I choose to go ahead and offer it right away anyhow, maybe they get a little entertainment from digging through it.