Still present in 1.13 release. From looking at similar bugs, it seems that if waterloggable blocks are adjacent to water, or other waterlogged blocks, they'll be loaded in as waterlogged. This can create a sort of chain reaction effect where if you have say, a ceiling made of half slabs with even a single block of water above one of them, all the slabs will be loaded waterlogged. Very inconvenient!
Still present in 1.13 release. From looking at similar bugs, it seems that if waterloggable blocks are adjacent to water, or other waterlogged blocks, they'll be loaded in as waterlogged. This can create a sort of chain reaction effect where if you have say, a ceiling made of half slabs with even a single block of water above one of them, all the slabs will be loaded waterlogged. Very inconvenient!