I know I'm going to get completely flamed for this. But since you asked a direct question and it was clearly something important to you, I just wanted to know what kind of clarification you were given.
The RY4 description says it includes caramel flavorings. If FSUSA uses Flavourart exclusively, and the RY4 includes the Flavourart caramel flavoring, then there is diacetyl in it. See: Diacetile - Flavourart. La sartoria degli aromi
If FSUSA does NOT use the Flavourart caramel for their RY4, then it does not include the diacetyl listed in the Flavourart description, so I'm wondering if he explained where the caramel flavor comes from. I realize this may seem nit-picky, but it's important in the context of this discussion and where all of the drama (particularly in regards to my position) comes from.
And before FSUSA fans jump all over me about this, please understand that I am not accusing anyone of anything. I am just CURIOUS and asking (what I believe to be) a valid question.
They aren't giving you the recipe for the love of holy things.
Does a wine with a "nutty finish" actually have nuts in it?
Yeeesh!