Shield dont produce "knocback" effect anymore when a mob hit it

So , what the title says , in previous versions , untill 1.13.2  if you were protecting you with the Shield and a mob hits you , they would go back , making like a "knockback" effect , like a "rebound" . a bounce, i dont know how to explain it properly , i speak spanish , english is not my main language , but well , i will put the video of what i am talking about , down 

 Video 

If there is any error , or something wrong in the post , please let me know so i can fix it , thanks for reading ♥