Sugar Cane can be planted under water, if placed on an edge block

As attached in the screenshot; Sugar Cane can be planted under water, as long as there is another water block diagonally below the block the Sugarcane is used on.

It seems that the Sugar Cane is checking that it is being planted next to water, but failing to ensure it is not currently submerged in water.

The Sugar Cane will not break with block updates.