All bunnies are different. Even from the same litter, somebunnies will have issues with pellets and hay at first, and others won't.
Definitely agree if a bunny is not yet 7 months, that the bunny should get free choice pellets and hay. At 7 months, I cut down to 1/4 cup plus fresh veggies. I do have small breeds.
I don't feed veggies until 6 months, but that's just me. Others have started as early as 4 months. I feel 8 weeks is way to early. It's only been a month since the baby started pellets and hay (usually they start getting weaned at 4 weeks), so he needs a bit more time to let his system get used to what bunnies should eat, not Mom's milk.
There are lots of different opinions. It's finding what's right for your bunny that counts.