I'm not disagreeing here, but I want to bring into consideration also the "momentum factor".
If you're thinking it rationally, what Billy said is completely true. That's the same school as the idea: "You're playing alone there, against the balls and the table and the situation in it. Forget the opponent".
I'm sure many pros think like this, but I'd guess there must be about as many who think differently.
The other "school" think it more as a fight, and the psychological part plays a big part in it. If you're down and steal couple of racks with some aggressive shots, you might gain the momentum, the confidence needed to steal the match. At the same time you shake your opponent, as we are all humans after all.
These things in this category affect more of those who play more with their emotions and intuition. For example Earl and Mika would probably in most of their games think a bit like this.
Then those more methodical and rational players, the patient ones like Ralf for example, can be put into the first category, where keeping composure and staying as "the master of the situation" are what they wish to be when they perform their best.
So I'm not disagreeing with Billy, just wanted to bring the other side of the story into picture.
I recall reading several years back a BD article from Mike Sigel, where he said just like Scott had said before Billy had disapproved.
Mike pictured a shot (iirc, 4 ball in head rail, whitey somewhere in the other end) and wrote that if he'd be 0-4 down, without hesitating he'd go for a long bank and try to get the momentum and the rush needed for the haunt. On the other hand, if he'd be 4-0 up, he'd go for the safety not to give any easy chances.
Myself, I tend to be mostly in the first category with Billy, but have experienced both styles various times. Both in the winning and in the losing end
Lastly; this idea is not to play against the highest percentage shot, but we have to realize, that the highest percentage shot varies as we are emotional human beings.
If we are full of adrenaline and confidence, that long bank might feel better than the safety. I.e. Mika and Earl might go for it even if they'd be up, if
they feel it better than the safety, which some other, as good of a player, might choose in that situation.
What Mike (and Scott) probably meant, was that by going for the aggressive instead of the safety when you're down, you give yourself an order to trust yourself and by taking some risks see it as "the highest percentage way" of winning the match. Even though as a single shot the safety might be bit higher percentage, in long run, for winning the match and gaining what is needed for that, you might have to choose the aggressive option.
Especially, if you're that emotional player who needs that rush.