When you summon a falling block with a negative time, NoGravity and if the block you are summoning it on is the same as the type of falling block your are summoning, then it creates a ghost block.

Command:

/summon minecraft:falling_block ~ ~-1 ~ {Time:-10000,NoGravity:1b,BlockState:{Name:"_____"}}

Steps to reproduce:

1. Walk onto a block
2. Enter the command with the _____ replaced with the block id of the block you are standing on
3. The ghost block appears under you

What should happen:

The block shouldn't turn into a ghost block