[tux1968]

You still pay the cost in processing time of the optimization tool with every real time request. Pug is adding in unnecessary HTML elements which the next step in the pipeline removes. It's clearly inefficient.

Whether that is really important is another question; probably in the big scheme of things it's not worth worrying about. But I wouldn't dismiss it without knowing for sure that the costs in complexity to Pug are actually significant. That would require someone who knows the codebase to comment.