I viewed his little creation as "extra credit". It shows he knows Sass/CSS and makes him standout from other "boring" interviewees that may have possessed similar skillsets.
Why not make it about their brand? It shows his desire that he wants to work there, and it's also clear he just made this. It isn't some cool thing he did awhile ago and is showing many different companies in interviews. He wants to work there, and that initiative shown will go a long way (and was successful, in this case).
Worst-case scenario is that he doesn't get the job but spent the night learning more about pseudo elements and how the interact with other elements. That's a win-win.
Why not make it about their brand? It shows his desire that he wants to work there, and it's also clear he just made this. It isn't some cool thing he did awhile ago and is showing many different companies in interviews. He wants to work there, and that initiative shown will go a long way (and was successful, in this case).
Worst-case scenario is that he doesn't get the job but spent the night learning more about pseudo elements and how the interact with other elements. That's a win-win.