Kickstarter, I thought, was different in that you could change your perk level up or down at any time because the money wasn't transferred till the end. I never tried getting multiple perks on Kickstarter (and I'm not sure it's possible under the same registration), but I have on Indiegogo. Even under the same registration, it seems that the different donations are counted as separate "donors."
Doing some of the Kickstarter fulfillment for our most recent Kickstarter campaign, I can tell you that the same people/users come up multiple times under different donation levels. It's annoying when I send out a perk and then later, I see that the same individual also has a different perk due them in another donor level. I could have consolidated shipping costs if I had noticed the same individual appeared multiple times.
In our case, the number of these duplicate donors is pretty minimal. Out of 788 donors, I'd be surprised if more than a dozen are duplicates.