Why is "MRN Data Models and Elektron Implementation Guide" missing field messageType

The main pdf documentation "MRN Data Models and Elektron Implementation Guide" does not mention this field at all. There is a discussion about the field in the N2_UBMS comparison page which is missing from the pdf documentation:

In MRN, the classification is defined in following JSON fields.

1. messageType field, an integer field that use the same enum value as FID 3 of N2_UBMS.
2. urgency field, where 1 is an alert and 3 is the newsbreak story article. The number of take is then defiend in takeSequence field.