INA219 with L298N POWER LOGGER
The INA219 gives you the instantaneous current and voltage at a given moment in time, whereas your DMM shows you the average over a period.
The L298N is giving out a PWM waveform that is rapidly being turned on and off.
You see where this is going?
Your Arduino detection will be giving you either full power or no power (or somewhere in between owing to the low-pass filter effect of the motor), pretty much randomly, whereas the DMM will give you the average over a number of samples.
You would need to rapidly sample the PWM signal over a period of time and calculate the average to get an idea of what the current and voltage might be.