This is as old as the hills. Even when DXTn was knew, they added DXT2 and DXT4 as placebos just for pma. The formats are identical to DXT3 and DXT5, but they were added to be useable as metadata for when the alpha had been premultiplied or not if you loaded them as .DDS files. (By checking the type)
So it should work on anything. If some card or other can't do it, your graphics will be a bit darker, but I wouldn't sweat it personally. That link you have might even refer to DXT2/4 support as opposed to blend modes.