I think what they mean is that there are no blocking functions in the standard library except alert, prompt, and confirm. ( are there any others?)

Yeah, you can call async functions without specifying it as such and the script will just carry on regardless of how you're handling it. Totally weird, but also pretty cool. When I first started some 20 years ago that was a major foot gun for me, coming from PHP where functions always returned before the next one was called.