This is much more often going to be true because the dispute was never made in the first place, because of the risk it would entail to a low wage worker. They cannot afford—for reasons of time, money, health, education—to even threaten to take an employer to court.
Your argument sounds logical, but is unfortunately unaware of how real world pressures distort systems for recourse.
However, the reality here is not likely that a sandwich shop employee would have to “threaten to take an employer to court”.
The most likely scenario is that the hiring manager doesn’t even realize that boilerplate is in their employment agreement. The second most likely is that the employer grumbles about the employee leaving and that’s as far as it goes.