Whatever train trip you take, there is *always* a new data headache

Next week I need to take a TER train Culmont-Chalindrey - Mulhouse. This is the Paris Est - Troyes - Mulhouse line, which is compulsory reservation *only on the bit into Paris* according to this: https://www.sncf-connect.com/aide/reservation-bord-des-ter-fluo

But timetables and the Interrail app think its comp res throughout

I am going to try my luck without a reservation