As showN in the attached video clip, it is possible to place and pick up a water source when pointing at the sign, but not when pointing at the other blocs also in contact with the same source.

You can't really tell in the video but I am trying to pick up the water when pointing at the nearby cobblestone with no success. I can also that I'm playing on iPad with a Bluetooth controller.

The expected behaviour here is to be able to pick up the source when pointing at the water, independently from the targeted block that is behind that water. Just like on Desktop Java.