Updating the BlockState of a Waterlogged block does not trigger a physics update like it does when one updates the BlockState of a water or lava block.

Consider a fluid block suspended in an unstable, un-flowing state by cancelling {{BlockFromToEvent}}s. One may force the fluid block to flow by manually placing a block adjacent to the fluid block (causing a physics update). Attempting to automate this process is the following code:

if (block.getType() == Material.WATER || block.getType() == Material.LAVA) {
    Levelled levelled = (Levelled) block.getBlockData();
    levelled.setLevel(1);
    block.setBlockData(levelled);
    Bukkit.getScheduler().runTaskLater(PLUGIN, () -> {
        levelled.setLevel(0);
        block.setBlockData(levelled);
    }, 1);
} else if (Util.isWaterlogged(block)) {
    Waterlogged waterlogged = (Waterlogged) block.getBlockData();
    waterlogged.setWaterlogged(false);
    block.setBlockData(waterlogged);
    Bukkit.getScheduler().runTaskLater(PLUGIN, () -> {
        waterlogged.setWaterlogged(true);
        block.setBlockData(waterlogged);
    }, 1);
}

The expected behavior is for the fluid block to begin to flow. Indeed, the code works perfectly for water blocks and lava blocks since changing the Levellable level causes a block update. However, the same concept when applied to Waterlogged blocks does not work: it simply does not flow, whereas manually placing an adjacent block does cause it to flow. Additionally, forcing updates via BlockState#update on both the Waterlogged block and all adjacent blocks fails to cause the Waterlogged block to flow. I do not believe this is expected behavior.