Hi Regina,
Some of this will be discussed by our standards representatives via defect report to the Office Open XML (ISO 29500) committee with an eye to improving the text in this area, including consideration of how this can help other standards interoperate (like ODF). You can refer to this DR here:
As for a complete set of rules for this particular feature, we believe how Word chooses to layout a document given the provided inputs is an implementation detail of the client application that Word open specifications won’t be formally/publicly documenting.
Tom