"Real chicken" is contrasted with chicken or poultry by-products to lead consumers to believe that "real chicken," (whatever that is), is superior to by-products.
No definition of "real chicken" is usually made by producers making the claim.
If it is just chicken meat, as implied, it is far inferior to the meals.
In fact, in the wild, which is the model we should be looking at if health matters, carnivores eat the entire bird, other than the feathers.
That is in fact what chicken and poultry meals are made of (minus heads, beaks, feathers, and legs).
The ideal pet food ingredient is fresh whole chicken, next best would be meals, last would be "real chicken" (assuming that is chicken meat only).