X12 Standards and Segment/Loop Ordering

Why oh why did the X12 committee for health care define some standards that allow some of the segments and/or loops in an X12 document to appear in any order?  The doc specs define the order in which all these things must appear in an EDI file, but some rare segments/loops have the same relative position, meaning that those particular items can actually appear in any order relative to each other in an X12 file (e.g. in the 4010 837P see the 2420{C,D,E,F} loops).

Darn that makes it hard to parse into XML and validate.  I’m guessing (just a WAG here) that about 99% of the X12 standard definition for any given document defines a well structured order.  What was X12 thinking when they allowed so few of these things to be randomly ordered amongst themselves?  That is just nuts.

If there is a valid rationale for that I’d honestly like to hear it.  I’ve spent the last two days cursing it…..