The udon dough recipe indeed use more salt than pasta and bread dough. It is not a mistake. Salt strengthens and stretches gluten in flour, producing distinctive chewy texture in the final dough/noodles.
When we cook udon noodles we cook it in boiling water. We do not add salt in it. Cooking process removes most of the salt in the udon noodles.
Here again the correct udon dough recipe;
300g Japanese udon flour or all purpose flour, shifted
15g sea salt
146 to 135g lukewarm water (use more water during dry and cold winter time)
Potato starch for dusting
Udon noodles made from scratch has a heaven texture and flavor.