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.
That's a common risk management tactic. It's literally in the textbook. Likewise, the Vice President flies on his own plane, Air Force Two, and never Air Force One. When the President and Vice President have to be in the same place at the same time, someone else in the chain of succession has to be kept somewhere else; most dramatically, when the President addresses a joint session of Congress, as in the State of the Union address, one cabinet member is named the "designated successor", is not allowed to attend, and is provided Presidential-level Secret Service protection for the duration.
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.