Fingerprints aren't fool proof and pretty easy to fake if you have just a bit of time. Also one could theoretically clear at the GE machine and hand off your passport and slip to someone else. Most e-gates do the same problem essentially using a computer. You scan passport and fingerprint/biometric, the gate opens, you step forward, the gate closes behind you, a camera verifies your photo and the final gate/door opens allowing you past. Ensure that the person who has processed the passport is the same one actually going through.