Well if it works consistently, I don't see any problem with that. If they have a clear theory of when to add "photorealistic" and when to add "correct number of wheels on the bus" to get the output they want, it's engineering. If they don't have a (falsifiable) theory, it's probably not engineering.
Of course, the service they really provide is for businesses to feel they "do AI", and whether or not they do real engineering is as relevant as if your favorite pornstars' boobs are real or not.
Of course, the service they really provide is for businesses to feel they "do AI", and whether or not they do real engineering is as relevant as if your favorite pornstars' boobs are real or not.