I've thought that's the way it was pronounced since I first saw it in 2006. I mean, look at the avatar.
How is it pronounced?
.....Adam, I got stuck with the nickname mule at work, way back, around 1985....I was married at the time, and showed a picture of my then-wife to some friends at the railroad....she was an absolute knockout in the picture, and one friend said, "man, how did you ever get a wife that looks like that?, you must be hung like a mule"....thus, the nickname was established, and the "misnomer" spread like wildfire.....
.....when I bought a computer in 2000 to follow the stock market, I had to choose a handle at hotmail....the same friend suggested mulester, one who takes care of, and trains mules....little did I know if you run a dictionary.com on the word mulester, it says "no such word", and suggests "molester" no less, wow....it was too late to change handles I'd established everywhere at that point, so, here we went.....