Wither Skull. Many Issues

What the bugs are.

• When I summoned a wither skull it doesn't move it just stays.
• You can place other blocks in it. Shouldn't it explode when you do that?
• When you put TNT they shoot off and they move to align correctly and the particles are not rendering to the wither Skull but about half a block above it.
• It gets pushed by TNT when it explodes under water.
• Z happens when it is perfectly in one block.
• It can get pushed by lava and water.
• fire Charge goes right through it as if it weren't there.

  see videos

  I used the command

/summon minecraft:wither_skull