/replaceitem does not work on Suspicious Blocks

Why does it not work. if this is intentional I will go insane.

 

ok so they want me to tell people how to do it even though the video shows exactly how to do it this is absurd

 

step 1: open minecraft

 

step 2: go to a world

 

step 3: place SUS sand or SUS gravel

 

step 4 try to use the command i used in the video but use the coordinates of the SUS block

 

OBSERVED RESULT: it does not work

 

EXPECTED RESULT: it should work