Hari is showing us how to lightly trim a full, short length beard. The end goal of this trim is to maintain a natural cheek line. This will make the beard appear thicker and have a nice round shape.
Hari makes sure not to trim the top of the mustache. Just like the cheek lines, the longer hairs on the top of the mustache will make the stache itself appear fuller. Unless you're trying to grow a large handlebar mustache, keep the hair overlapping the upper lip trimmed and shaped.