I don't think that you do have to switch AF back to the shutter button. I have the AF set to the back button on both my 5D, my 50D, and my 1D4, and I use a remote release on all of these bodies and it works fine and I have never set the AF back to the shutter button.
I think this is correct. I have used a set of Phottix triggers as a remote and they worked fine. But I usually just use the delay timer. If I haueve live view enabled, the mirror is already up and everything is still, so I just use the shorter delay time. And, if I am plugged up to my DSLR Controller app, I have the big display on my phone or tablet and a remote shutter release right on the remote screen. Couple that with the short delay and it's hard to beat.
I might be making a bad assumption, but even though this was not made clear, I would assume that the statement re: remote shooting had to do with the fact that if set to AF ON, using a remote the camera will not auto focus. Of course for many (most?) remote shooting situations, you don't want to the camera to change focus anyway, it would be a preset focus, so it was a strange way to phrase it.