Following the tutorial, the instructor inserts the black faces and creates a vertex group just for the vertices inside the inset. I’m trying to do same thing (not did exactly same teacher steps) and it seems more vertex than selected are added to the group (The vertices inside the inset and the ones in the frame).
If I deselect everything after doing the inset and re-select the vertices and create the group, the group is created with the correct vertices.
Is this as intended or a bug?
Video demonstrating it: