I have seen the difference. I let a friend have some 3 week old chicks. Both those, and the chicks I kept, had been wormed at 2 weeks.I gave my friend my worming schedule. She chose not to follow it, but she did feed the same as I do.When I saw those chicks at 5 months, they were unrecognizable as being from my flock.My pullets were laying. My friend's certainly were not, and did not lay until 8 months old. Those chicks matured out at 2/3 the size of mine, with terrible feather quality.That's a lot of worming.... have you ever run a control batch of chicks next to the regularly wormed ones to see the difference? I'm curious if it makes a huge difference.
I accidently did that with some chicks in regards to feed. I had a hen raising three chicks she hatched. They free ranged with the hen and had a pan of chick starter that they could acess, but the adult chickens could not. I needed a turkey poult tutor and pulled one inside to the brooder. About three weeks later, I noticed that the chick in with the turkey, which was getting 30% wild bird starter was nearly three times the size of the two still with their mom. I took the other two inside and in another month, the difference is not noticeable.
I would like to see the difference your schedule of worming makes in side by side comparison.