That did not work for me (though it did on the park rape scene), last time I played the panties option was not in the game, so I did not even thing to try, and fought him. The Shower scene is still locked on my computer. The same thing with mom and the Ectopus scene. Beating it did not unlock the alternate scene in the gallery. So in the save where I saved mom and fought Dash, I have 2 scenes still locked.
While I don't mind not letting it unlock until you do it, it would be nice if it was unlocked even if you did not do it on that save, universal unlock. For example, if you reloaded a save to try both options. I suppose that is one of the down sides of doing the gallery in the computer, rather than on the main menu. Not to mention 'ending the game' at the end of the new content, it would be nice if we could still run around and see if there was something we missed, or just to look at the computer...
Oh, I also just noticed that the quest log says I still need to get the cheerleader outfit, when I have already delivered it, and was about to go meet them at the field.
Neither the 'H' key, nor the middle mouse button removed the dialogue box, you have to click the button, was that intentional?