If you import an image from a format that has many channels, say 13 channels, that creates 13 images each of which is a single channel, one of the 13 channels. You can then do whatever you want with that data, for example, creating a synthetic RGB image with 3 channels, each of which is taken from one of the 13 single-channel images using a join. The JOIN dialog is the easiest way of doing that, as shown in this example.
I've just checked the .zip file you attached, which is a multichannel TIF. It imports into 9 as a four channel TIF. Don't know why, but I've reported it.