I know it does make the download "smaller and harder to decompile" but by what means?
At first I assumed it would resize pictures and compress audio (in case I have a 10 megapixel background image I forgot about etc). It could also delete unused things I added to the project. Another thing it could do is renaming assets (e.g. to "3241.ogg" instead of "Super Cool Corporate Music Bought at xxxxx.xxx for five dollars.ogg").
Does it do any of the above? If not, what does it do?