Just have to say, a half gram dab is a fat dab. I'm sure some people do vaporize all of that at once. However, even with complete inhalation and 'swishing' it in their lungs, they will be wasting a lot of it on the exhale.
'Swishing' in their lungs? I've never heard of that, how does someone even do that?
I presume he's referring to repeatedly exhaling and inhaling a tiny amount to keep circulating smoke in the lungs without losing any to the air. Can't speak for its effectiveness.