Master Wong does his best to show WC, I mean, the elbow could work, but it's not that good of a technique against a boxer. What if the elbow doesn't time or land right, or if the boxer throws a body shot or hook, the elbows really inefficient at guarding against body shots or lower targets, which means it'll leave you open to get KO'd. I give him props for trying though... but yeah, the elbow COULD work but it's not highly probable, and shouldn't be "the main tool."
Actually most Wing Chun fighters I met who are pretty good are either 1% highly skilled pure traditionalists (which are very rare, most of them suck), or they are WC fighters who have a decent background and study in boxing and are doing WC at the same time. The ones who can box really well and get really well at WC too are usually the more skilled fighters obviously. I know a muay thai dude who does wing chun as well and he found his way of putting them together really well. His old school muay thai background and experience combined with the more softer wing chun technique and concept balanced out quite well, but it was only because he was really good with muay thai and put in an equal amount of practice and dedication to his wing chun studies.