I don't know what their exact process was, but I'd guess there was just a non-tech phone screen before the onsite. It's a tricky balance, some people get insulted if you ask them to complete a pre-screen coding exercise. "I have 15 years of experience, stop wasting my time!" On the other hand, I've interviewed a few people with that much experience, supposedly code-writing lead engineers, that couldn't write the code to insert an item into a sorted array.

There are a lot of people who have more credentials than skill, which isn't easily detected by looking at a resume.