When placing water sources on untouched land it flows out the 7/8 spaces in all directions.  When building up a new surface, or modifying the previously working surface the water flow changes when the source block is placed.  In my example pictures: I am building a multi tiered farm that worked in previous version years ago where a source block was blocked by a piston, when the piston releases the water it would cover the entire farm.  In the current version the source block starts to flow and then goes in one or two directions only and does not cover the entire farm as it used it.