Sounds like lore. Won't let them fly on a plane together? I hope they don't ride in the same car to the airport since that's even more dangerous. (see my point?)

It's possible only 2 people know it since 3 can't keep a secret. More likely anyone that knows it has signed NDAs on top of which they each know two versions of the same recipe with an indistinguishable flavoring difference due to a minor quantity differences. Either recipe were to get out it's obvious who leaked because the master copy is in the vault. The exact quantities are like a watermark that gives away the leaker. At any rate, if you have golden handcuffs you don't leak due to self preservation anyhow.