Yeah, see, it's not a question of getting fed up and leaving before you get fired, it's an issue of an employer creating a work situation -- with unreasonable job requirements (which you didn't sign on for initially) -- such that they put employees into a position that they are forced to quit rather than be fired or laid off. It's an underhanded employer maneuvre that "constructive dismissal" is supposed to guard against. Like Evo's situation of being handed an impossible task, and ensuring that the task is entirely impossible by making them sign documents in which they agree not to work over 40 hours a week in order to meet the demands of the unreasonable standards.I can't find anything like that, nor have I heard anything like that in the US before. I don't think there's any law protecting you if you get fed up and leave before you get fired.
In other words, the employer is deliberately, and rather clearly, setting up a situation in which "dismissal with cause" is viable or people simply quit because the situation is intolerable. That's not allowed here. It's not really fickle.