I think justsomeguy's idea was that, to learn how to gybe the asym, practice without the main, so that complexity is significantly reduced, so that you can see and control the chute, and not have to worry about the chute while trying to gybe the main, etc. Once you've got a good bit of practice, and you've got a feel for how the chute behaves, and the quirks of your setup (lazy sheet getting caught, etc.) then you'd have a good base, and could start playing with the main up for better speed.
When I started flying my asym, I do it solo, and I would do it on really light air days. This was partly because the halyard was mounted at the mast head, and that's not right for a fractional rig with uppers only going up 7/8ths or so. That, and the wind was so light, I kinda had to drop the main to get the spin to fill. Now that I've played with it, lowered the halyard to 6" above the hounds, and added a cam cleat down lower on the mast (as opposed to a horn cleat above the gooseneck) I'm ready to start flying that puppy in more fun conditions! If only it weren't off season… Then again, I couldn't move that halyard block until I hauled out and dropped the mast…
Brian