Water and the blocks are not entangled properly, To match reality, water should be pushable but not pullable. Here's a list of proper interactions. Water can be contained in a fence surrounded by blocks and disappear when it should have logically been contained and moved in it's container. 

Sticky piston facing east into waterlogged stair block facing east: water is both pushable and pullble.

Sticky piston facing east into waterlogged stair block facing north/west/south: water is pushable but not pullable.

Sticky piston facing down into bottom half waterlogged stair block: water is both pushable and pullable. 

Sticky piston facing down into water source block: water is pushable not pullable

Sticky piston facing into water source block facing east/west/north/south: water is pushable not pullable.

Sticky piston facing up into water source block: water is pushable and pullable

Sticky piston facing down into bottom half waterlogged slab: water is both pushable and pullable. (though this could also be considered an illogical interaction anyway.)