Eddie Van Halen holds it that way, and it seems to work out pretty well for him. Pick positions are kind of like batting stances in baseball. There is a preferred way to do it, but really whatever works and it comfortable for you is the best way to go.
I can see advantages to holding it that way, and disadvantages. But all in all, a perfectly sensible way to hold it. You can pick a note and quickly tap with your index finger lower down the neck, that is nice.
I think I will use that. Not all the time, but it clearly has its advantages. No reason you can't hold it one way sometimes, another way other times.