But if you lost your wallet and phone they could go shopping with all of your cards anyway (if they are contactless). I’m not sure why they would bother transferring money from one of your debit cards in the wallet to your Monzo card rather than just using your debit cards directly?
I’m not sure why further security is needed for a deposit as that can only result in you gaining money? For a withdrawal and for general privacy pin/fingerprint access could be useful.
People should have their phone locked down though given it is probably the one item that could give someone almost complete access to your life.