TNT Explosion doesn't give full amount of blocks break

Go in a world and place 5x5 size floor using coblestone. Place a TNT on the coblestone and ignite it.

 

After the explosion of the TNT , pick up the blocks that it drop . U wont get the full amount (25) of blocks that it destroyed.

 

It should drop the full amount of blocks destroy.(Like Minecraft Java Edition)