A) no where on the article that I could ctrl+f 'screen tearing/tearing/tear'. So you're putting words into their mouths about them running TR @ 40-60fps without tearing. Having said that, tearing is less frequent below target refresh rates, but it still occurs, just less than having frame rates higher than the refresh rate.
B) I mentioned you can remove screen tearing entirely if you enable v-sync, but that will result in juddering and latency in controls. Please read the following:
And last but not least DF mentions v-sync in the article itself. They make no mention if it's adaptive or full v-sync. But I know if it's the latter they will never experience tearing. If it's the former, they will eventually catch footage of the tearing occurring.
You need to do research on the topic yourself. V-sync and screen tearing has been around forever. It's why they're developing technologies to combat it:
http://www.anandtech.com/show/7582/nvidia-gsync-review