Falling block breaks blocks when in contact

I was making falling block to be summoned at the player via /execute and I noticed that there is a small gap between the falling block and the ground under, so I changed the command to; /execute @p ~ ~ ~ summon falling_block ~ ~-.01 ~

{Block:grass,NoGravity:1}

instead of summoning it exactly were the player is. And if I was standing on the same block that is in the Block: tag, the block would be broken and the falling block would be floating above.

You can reproduce this 'bug' by putting the command I mentioned above in a repeating always active command block.

I have tried this in single player and in multiplayer, they have the same results.