Same here, I don't even know how these bonus rounds that they're talking about look. In what way do we measure skill? Skill in what?
An example of a skill based gambling machine could be a pinball table made in such way to work like a slot machine and pay people for high scores. Usually a slot machine has just one roll button/lever and the only thing you can change is the stake, number of slots, or the theme, you can't really react to what the machine is showing. To allow for skill test the machine would need to work like an arcade machine, allowing you to test memory or reaction time. I'd play something like that if I had the chance.