My German Shepherd would do anything for a piece of chicken. He would suddenly seem to understand English. My boxer couldn’t care less for treats as a motivator - positive attention was the absolute only way to mold behavior. Having had the GSD first, it took some adjustment for me to learn to train a dog that just didn’t care about food. The breeder later told me that was entirely typical of boxers.
I grew up with a boxer that was almost completely food motivated. The neighbor's GSD was almost completely play motivated, and would skip meals in the hopes that someone would just. throw. the. ball.
Your breeder's statement is like stereotyping human personalities by ethnicity or gender - something may show up strongly in the statistics, but it's a poor tool to apply when interacting with individuals.
Dogs that are not only in it for the food are a useful counterexample, because it trumps the sweeping “only.”
That -some- dogs are in it for the food doesn’t move the needle in the debate one way or the other.
Great read for people looking for a more rigorous treatment of dog behavior and psychology.