This diagram from Flavor West themselves states that Diacetyl or Acetyl Propionyl is NOT added in the flavors where butter, cream etc.and caramel is part of the taste. Instead "harmless” Acetoin is used.
However, please note that some studies have shown that Acetoin, in some cases, can transform into Diacetyl but this rarely happens after the flavor has been mixed with nicotine base. If you don’t want the slighest trace of Diacetyl you will want to avoid these natural flavours and maybe use a synthetically produced flavour instead.
In this context it is important to remember that we are talking about flavours/aromas where the content is not vaped on it’s own but added into the nicotine base in a ratio of about 5 - 15% and that even within the flavour/aroma, Acetoin is just a small part of the mix.