Armor Stand Pulled in when 1 block is pulled down

Hi im a YouTuber that make buildhack Why is the armor stand pulled down when it only has 2 blocks of space but when I pull a block with piston why is the armor stand pulled down and stuck down there? I pushed it from above and the block was pushed Right from the top of the armor stand's head. The question is why does the armor stand slide down and when it is pushed, there must be only 1 block of space left, it should be black, I suggest this bug be fixed and Under the armor stand there is an enchantment table.