I have ridden some races where I think the organisers think marshalls are there to point the way and stop folk cheating. They are there to protect the riders and summon help if needed.
as we run two courses at the same time we use marshals to ensure the right rider goes the right way at splits, the aim is to stop the less skilled rider entering the technical sections on the main course
I didnt see any marshals with flags.
the organiser should have been gripped by the commissaire, clearly in the rules as a requirement. I got my mum to make some out of old curtain material

