My Fibaro wall plug tells me the “Power” value correctly, in Watts.
I indeed also have 2 “Power” fields, one is always wrong, the other one is correct.
I usually do trial and error to find out which one of the 2 Power parameters is correct.
It’s strange it does not update for you. You could try looking at the parameters of your plug, how often it reports power usage.
For me I see it +/- every 30 seconds, also visible in the zwave logs.
I have the same set-up, an sms is sent once the washing machine is done (no power used).
I then also shut down the wall plug and put this in the IF statement to stop the scene from running.