Simple. It's bait and switch. They're willing to give the Diamond Visa to people with better credit, but they also want to pull in applications they can divert to the Classic Visa. They couldn't get anyone to apply for the Classic Visa at 35%, especially the people who qualify for better (and I know 30% isn't much better, but Aspire gives them higher limits too.)
I've never heard of anyone receiving anything from Aspire other than the Diamond Visa. Regardless of what type of card you get from Aspire, the interest is too damned much. They have excellent customer service, and they post payments on time. I liked them when I had their card. Still, I wouldn't even consider applying for any of their products unless I were damned sure I could pay off my balances every month. Otherwise, you'll be older than me before you can pay it off.