thats most likely where in the glitch lays, I tried i donno how many times to do it with a arrow from numerous locations all over the fort, just about every time I was caught. and Never once got the bonus using arrows. The first time I used the statue, I got the bonus. Done it this way every time sense, and have always gotten the bonus.
I killed her with an arrow, hiding in the most stupid location imaginable, and nobody ever saw me. I was ducking behind a decorative bush next to the door that faces the balcony directly, a couple of feet away from the bored little kid in the back. After the murder, Veezara showed up and I was able to casually walk out of Solitude with no problem.
But the gargoyle story you just told made me wish I did it that way instead, that sounds really cool.