The bug

If a waterlogged block flows into a specific direction, it doesn't move entities, as opposed to a normal water source block.

Original description

So ever since the latest 1.13 (18w10d) that's has lately been released I noticed a big issue with the new water mechanic: All types of slabs, stairs, fences, trapdoors, and ladder (when you right-click the water bucket into the same space) the direction of the flowing water does not seem to be able to push any mobs when they're standing it and as well for the items when you throw them into the flowing waters direction, it doesn't seem to move at all.
I even tested it with my own player to see if the flowing water would only affect players and not effect mobs and items, miraculously though, when my player jumped into the flowing water I didn't move at all in any particular directions. It's a bit queer that the said flowing water direction doesn't seem to do any thing hope that gets patched very soon before you fully release 1.13.