Um, have you read our USBRS wiki?  (Full disclosure, I am substantially its author; other OSM volunteers help enter the route data, one recently from Germany!).  Please see https://wiki.osm.org/wiki/USBRS and if you care to read about the German guy who helped, see https://community.openstreetmap.org/t/aashto-s-usbrs-proposals-spring-2024-round-new-national-bicycle-route-proposals/110761 ).

What seems like it is happening is that a new category of "national" bike routes is emerging, namely these "designated by a national-level agency" (Grand Rounds / GR in an "All American Road" as part of the National Scenic Byway system, so designated by the US Secretary of Transportation).  See https://wiki.osm.org/wiki/United_States/Bicycle_Networks , the "Quasi-National" section (National is for USBRs).

Both national and quasi-national are agreed to be tagged with network=ncn in the USA, making them both red in Cycle Map layer (or pinkish in CyclOSM).  So, this was tagged ncn a few months ago, which made me think that a new "category" of quasi-national routes is emerging:  those which are All American Roads (or NSB, a subset of AARs).

Yet, it may be that your local view of the cycleway networks is "easier" to see GR as regional / purple, rather than national / red, since the Twin Cities have a rather complex confluence of USBRs 20, 41, 45 (MRT) and 45A (MRT-Alt).

There's a long history here, and lots of people (in OSM, in state transportation circles, at the national AASHTO level...) strive to get this correct (since about 2011).  However, I really want to hear local concerns / preferences.  Thank you once again in advance.