It comes up for me. Clicked big pre install button down the bottom left in battle.net program, first screen that comes up lets you choose the install location, select auto update option, default language and desktop shortcut. Clicked continue down the bottom right, next screen has the option to select install content, the second tickbox is for the high res texture pack and it lets me untick it.
Okay … so … I am not a Tech person by any stretch … but what you are saying is … even if I downloaded the entire package (higher GB version) … I can still choose lower graphic settings upon launching the game?