Color map with a 1-bit alpha: Missing? Disabled? Legacy? Deprecated? Defenestrated?

Link to same question on answerhub: https://answers.unrealengine.com/questions/318751/texture-with-1-bit-alpha-no-longer-an-option.html

Just wondering if I’m missing something or if the option to have a 1-bit alpha in a DXT texture simply doesn’t work anymore. Adding any alpha at all appears to just switch to the interpolated alpha scheme that doubles the size of the texture. Thanks guys!