From the article, speaking of the fly machine:
this machine puts your shoulder joint in an extremely vulnerable position, as it simultaneously rotates and abducts, according to Matthews. While this is especially dangerous for those with shoulder problems, using this machine can also cause injury in otherwise healthy exercisers.
I think that is a good point, at least for some of us. In fact, due to my occasional rotator cuff injuries I have been using no more than 30-35 pounds on the fly machine during the past few months, about half the weight I once used on this machine. I also do it last, at a leisurely pace with cooling down more on my mind than heavy exertion.