Universal buttons: bugs or feature

[Mark Smith]

Hello all,

Recently I decided to try out a number of different button styles to see which ones I liked best, and I ran across some odd behaviour with “Universal” buttons. First, there does not appear to be any style difference between an enabled universal button and a disabled one. With all other button styles there is a noticeable difference between the enabled and disabled versions. More importantly (perhaps) with all other button types if you depress the mouse over the button then move the mouse off the button and release it it does not fire the button. With universal buttons if you move a depressed mouse off the button and then release it the button fires. And this behaviour does not appear to conform to Apple’s user interface guidelines "The mousedown event is fired at an Element when a pointing device button is pressed while the pointer is inside the element.” 

Are these differences in the Universal button deliberate features or bugs? If features, why so? 

Thanks
Mark