Is your dog belching or throwing up?
I thought Science Diet’s “Small Bites” was the smallest size made until Casey’s breeder gave me samples of Diamond Puppy Formula to help switch foods. I remember thinking on the way home that this looks like dry cat food. It wasn’t until both he & Tessie threw up Beneful Snackers & Science Diet a couple of times that I realized the larger the kibble, the less likely they are actually chewing it and/or digesting it.
I couldn’t find a good article on this subject, so maybe it’s just what your dog prefers. I remember Zack preferred Science Diet’s “Small Bites” vs. Science Diet’s larger-sized kibble.