I fully understand the frustration. If you look at the official criteria, it is clear that these markers are eligible.
They are very much distinct, if you use the meaning of the word distinct as mentioned in the criteria (you can very easily identify these in real life). The location is usually easily identifiable using street view. So no reason to reject these. The question is, do they meet acceptance criteria, as the sole purpose of these signs is to explore the country on a bike, they meet two of the three acceptance criteria (good place to explore and exercise).
The purpose is not a simple direction to get from A to B, but to use the scenic route.
see also:
But unfortunately this is my opinion, and not the opinion of Niantic, and in the end they decide.