Actually you're making me have to repeat myself. Again, you haven't created a 5mb game and then added a 60mb addition to it. The game is not 5mb at all, its 65mb. The dll file in question is just as much part of the game as any other included files.
I suppose the documentation could be amended to say something like "games exported with NW.js will be at least X mb", but there's always a trade-off when choosing what information to include or highlight.