From what I understand, that paragraph applies to well documented cases such as 'St.' placenames in the UK. The consensus seems to be to expand directional prefixes/suffixes on street names regardless or not if this is what governmental agencies list them as. For example, (https://www.openstreetmap.org/way/114035456) is named 'Southwest Roy Rogers Road' despite it 'officially' being listed as 'SW Roy Rogers Rd' on RLIS and physical signs. Regardless, I encourage you to continue this discussion on either the forum (https://c.osm.org) or the OSMUS Slack (https://openstreetmap.us/slack) to allow other mappers to weigh in.