Updated the roads around here too. From all of the maps I checked it looks like Finlay-Manson stops at the junction at ~31km and then Thutade starts. Meanwhile the Manson Mainline starts on the south side of Manson River. Does that align with what you saw on the ground?
It all seemed to be signed Manson from starting at Finlay, continuing past the Thutade junction at 31km, and up to the Germansen Lake junction around 68km.
0km to 31km uses radio channel RR-12, the rest uses radio channel RR-8. Thutade uses a different radio channel going south from the junction at 31km.