Perhaps the policy was different many years ago, however since I can remember UA also has never seated employees (on pleasure travel) ahead of eligible, paid customers. A point of confusion may be when revenue passengers are standing by but only F seats are available at the gate (Y has checked in full). If the revenue passenger does not have the means to upgrade (money, certificate ....), the seat goes to the employee. However if the revenue standby passenger was affected by a previous irregularity (misconnection, cancellation) and not just wanting to fly earlier than ticketed, the gate agents generally make exceptions and start upgrading people for free.

Employees on business travel at UA, like almost every other carrier, get similar priority to revenue passengers.