The water flows even if trap door is closed after being opened

With the exception of placing a block under the trap door, Open and close a trap door doesn't update water.

To reproduce :

• Place a trap door blocked on all sides by a block except the underside.

• Place a water in this trap door (the water doesn't flow)

• Open the trap door (the water flows)

• Close the trap door (the water flows too)

• Result : It's not logical and It's technically a bug