Flowing water can go through moss block

Summary:-

Was testing moss block with water and apparently flowing water can go through moss block. 

 

How To Reproduce:-

1:- Place a water source and make sure the water flowing completely.

2:- Grab a moss block and place it on the flowing water.

 

Observed Results:-

Flowing water can go through moss block.

 

Expected Results:-

Flowing water should not go through moss block.