I think they're PPC too. I've never heard of anyone noticing CPM payment before from any AdSense ads, even though it's theoretically possible.
You are paid for impressions only if an advertiser buys inventory on your specific site, not if you just pick image ads as the default.
It really depends on your topic. CPM ads, even the site-targeted ones, are relatively cheap to buy in blocks. Movie studios, for instance, buys whole blocks on most entertainment-related pages for every movie. It's not really a matter of his site being targeted, it's just all sites in that niche. (But I could be wrong and he could have a very popular site.)