Most restaurants do not issue a device per waiter. One or two tablets live on a station and everybody uses them, which makes "who took this order" a genuinely hard question for most systems to answer.
Vestibel separates the two identities. The browser session authenticates the device; a short PIN authenticates the waiter, per browser tab. Two waiters can work in two tabs on the same tablet at the same time, and every cart mutation and audit entry is attributed to the right one.
Logging out in one tab deliberately leaves the other logged in — they are different people. A PIN locked while a tab sat idle is caught at the request gate, so a waiter cannot fire an order between being locked out and noticing.
When a drawer is handed over at shift change, the outgoing operator's tab sessions are revoked, because they have walked away from a shared device.