This is clever, and I got a good laugh out of their example video. The demo UI of "Double click here" isn't very convincing - I bet there's a version of this that gets people to double click consistently though.
Like in reCAPTCHA (v2 at least) where it asks users to click on tiles to identify common objects like bridges or motorcycles. Surely one could conjure up a fake version of this.
I've seen people complete actual CAPTCHAs that were something like "Click here exactly 10 times to prove you're human" so I don't think you'd need anything fancy. People wouldn't stop to question it and are used to doing much weirder CAPTCHAs without understanding what they're for.