That's not what he meant! In your example, x is defined once when the loop is initiated. What he meant, was something like this...
In this example y will always return 1 because it's reset to 0 before it gets 1 added to it with every iteration of the loop.
SuperStrict For Local x:Int=0 Until 10 Local y:Int y:+1 Print x+" "+y Next
In this example y will always return 1 because it's reset to 0 before it gets 1 added to it with every iteration of the loop.