I thought Boardwalk has 3 views available:
1) Standard View
2) Garden or Pool View
3) Boardwalk View
I don't think there actually is something called a water view.
Boardwalk View which is on the lake facing towards YC/BC, costs more money to book. It's the more expensive of the 3 room types.
So if someone *wants* a free upgrade from standard or garden/pool view to Boardwalk view - that's probably not going to happen. And it wouldn't be Disney's fault, unless the person actually paid for the Boardwalk view and was denied that view, in cases where a booking error or overbooking might occur, I expect Disney would possibly compensate the guest for downgrading the reservation.
Once we had an obstructed pool view at AKL, paying OOP direct with Disney, they "upgraded" us to a Zebra Trail - Sunset Savannah view. We've always had very good customer service at the hotels thankfully.