Employee Contributions vs. Employer Contributions
In most 401(k) plans, there are two main types of contributions: employee deferrals (taken from paychecks) and employer contributions (match or discretionary). Both types can be divided via QDRO, but employer contributions are subject to a vesting schedule.
This means that the employee must work for the company for a certain number of years before the employer contributions are fully theirs. If your divorce occurs before full vesting, some of the employer contributions may not be transferable to the alternate payee.

