Interesting points and I would agree if the routes were not recently publicised by Cambridge County Council, see below. Please bear in mind the vast majority of linear relations are not identifiable on the ground, eg most B-Roads, many public rights of way and most borders, from neighbourhoods to Great Britain’s outline. The parts of the relation are clearly identifiable as highways and comply with the wiki for "lcn".
The detail at https://www.cambridgeshire.gov.uk/residents/travel-roads-and-parking/active-travel-in-cambridgeshire/getting-started/cycle-routes-and-maps  under St Neots says Preparation by David Earl at frankieandshadow.com Copyright © 2023 Cambridgeshire County Council licensed as CC-by-SA2.0. Map data copyright © 2023 OpenStreetMap contributors, usedunder the terms of Open Data Commons Database License (ODbL1,0). You could contact the aforementioned David Earl who is the original poster of the route. He still seems active on OSM.
