Howto reproduce:
if you place stair (in my case cobblestone stair) underwater, then try to remove water using blocks, and you find out that's stair can be combined with a water source
Comments 5
As mentioned by Marek, this ticket seems to just be describing normal waterlogging mechanics: placing some partial blocks underwater causes them to become waterlogged, which means that they can also act as a water source.
This is working as intended, as per the snapshot 18w10c changelog:
Water can flow out these blocks, but can not flow into them. When full of water, they will count as water blocks for all gameplay (such as swimming).
All waterlogged blocks are a water source. Why wouldn't they be - they are created by combining water source and a block?