But if you have a labor shortage and low wages at the same time, that means that workers accepting work with a low wage aren't available, but the employers are keeping wages low anyway. (And in this context, poor working conditions amount to "low wages" because they decrease the value of the job to the employee.)

In capitalism, "labor shortage" means "the employers had better pay their employees more, or else they won't have the employees to compete against other employers who will pay more".