No, it is not.
For details about the watchdog timer operation, refer to the user's manual of each device.
Usually, a divided main system clock (fx) is used as the watchdog timer's count clock.
For example, fx/256 is used in the uPD780034A Subseries and fx/128 or the subsystem clock is used in the uPD784216A Subseries.
In the 78K0/Kx1, either the X1 oscillation clock divided by 16 or the internal oscillator divided by 4 is used as the watchdog timer's count clock.