I notice this after playing/watching this maps quite a lot.
Did some review and out of 10 games, 8 times the top players closer to the water, the rest are similar distance. It can still be the simple size too small, but I am 95% confidence about this and I notice the different before testing it.
Not only shorter walking distance to build a dock, in some cases could able to use TC to protect dock from attack with some wall or Mongol easily move TC fire in dock range… Not at Dunube River level, but I feel some other maps have this issue too.