Hurt Players with Resistance 5 or more appear like being damaged

When a Player (or Mob, I don't know) with Resistance 5 or more (which makes the Mob almost invulnerable, Exceptions e.g. /kill) get "hurt", they appear once red blinking, in the 1st Person the Screen "shakes" and a hurt sound appears.
Tested with Fall Damage.
May be only on Fall Damage. (I don not know.)