It's the same with that flowerhorn example he has just shown what the fish should look like as a adult then sent you a young fish of the same strain
With Flowerhorn it is completely different. The adult Flowerhorn picture he used is almost the highest quality you can find of that breed of Flowerhorn, that fish alone could cost several hundred to a few thousand dollars. By using that picture it is either implied that is the fish you are getting or it is one of the parent/brother. The fish you end up getting is not nearly as high a quality and will not turn out anything close to what show pic was. The fished base color and nuchal hump will be nothing close to what picture implies.
Now if the adult pic he used was the father or sibling then it would be appropriate to you it because it would be an accurate representation of what the fish would look like as an adult.