I think predatory is an acceptable term here. They are charging people for being overdrawn who aren’t by the true the definition of the term overdrawn.
As has been mentioned before if the pots where a separate product that would be different but if I have a £1000 in my account Made up of £250 account balance and 3 pots With £250 then if the account goes overdrawn by 10 monzo aren’t being charged and they are not losing any money. My overall balance remains £740 in credit.