There's no real reason that you couldn't use tie downs with an electric. Some models shouldn't have tie downs because of the engineering in the arms of the awning, but, the FF units can take some downward pressure with no harm. The biggest problem would be the attachment of the tie downs. I have a manual the comes down really low for the attachment of de-flappers and rigging the tie downs, then I can extend the arms to jack it up and then put tension on the tie downs. A friend has a newer FF with the electric awning and his won't go low enough for someone my size (5' 5") to reach it easily...
Most salesmen are of the opinion that they are 1) hard on the arms of an electric awning 2) defeats the ease of withdrawing the powered units and 3) aren't needed since with the simple push of a button you can bring the awning in in a flash in the event the wind picks up or you are leaving your sight for a while. In the event of having to bring the awning in in a hurry, tie downs would have to be removed before you could run it in.
I use tie downs on my manual so that in a moderately stiff breeze I don't have to go to the trouble of manually stowing my awning. If I had an electric, I would forego the tie downs and just press the "roll up" button inside
A quickly stowed awning is much more safe from damage than any tied down awning.