Ah ok, we’re talking about different things.
The fingerprint protection is a privacy feature, rather than a security feature. It stops people going into the app to look around but there’s extra steps that users have to complete before they can withdraw money, for security.
The PIN protection is on the way. But in the meantime, Monzo’s liable for any theft that happens because it’s not there. Which suggests there isn’t much theft because if there was, it would be a higher priority. And if you lose money due to the PIN not being there then (as long as you’ve followed the rest of the T’s & C’s), you’ll be reimbursed.