Rules 5.5.20 gives you the permitted permutations of must haves, plus a typical list that allows people to follow traditional one piece mast rigging principles. The rules do allow you to run all halyards internal to reduce windage or externally (not main Hayard) should you desire.
Section 5 refers to the Bermudan mast. 5.5.20 (a) 1 refers to the method of attachment and 5.5.22 refers to the heights of those attachments.
I can see why the confusion and maybe some additional wording within section 6 would clarify this. Not my Job, but this is to coin a phrase is a 'living' document. There has been a significant change with the introduction of this rig and sometimes wording gets missed. I am sure that it will be corrected in the near future. Always check for the latest document from the ISAF website. Ihope this helps.