Yes but if the employee is getting more at the new job then they were by definition underutilized and/or underpaid at the job they were "poached" from. Collusion amongst employers artificially limits employee earning power and cripples the invisible hand of labor economics.

Top flight employees should always be working at the edge of their abilities for commensurate pay. Anything less is an inefficient allocation of capital that hurts the industry as a whole.