In a nutshell: Why doesn Hazelnut/Almond flavoring taste like their namesakes?
I wondered about this one for a while. I now make almond milk on a regular basis, and often soak the almonds in water before grinding/straining. What I discovered was that there is a difference when I use cold water vs. hot/near boiling water. When soaked the almonds in near/boiling water, then the almond flavour that is the one like marzipan and almond flavouring (which I absolutely hate) was drawn out. This did not happen when I use cold or warm water. These are with the same types of almonds. So, I don’t think it’s just the type of almond, or that it requires alcohol (although this may be correct as well), but that the characteristic flavour of almond extract, requires heat to be activated. On the other hand, it does not come out when you toast the almonds, and that I can’t explain.