If you cast an Ender Pearl into the End Gateway portal (the one created after defeating the Ender Dragon, which sends you to the "Outer End"), the Attack Indicator and visible recharge animations do not use the proper Attack Speed.

Any item, weapon, or tool used to attack displays the same speed for both animations (approximately 0.25 sec, or 4 Attack Speed). However, the damage dealt does not seem to be affected by the indicator; spam clicking still deals less damage than waiting for the (actual, not the visual) recharge duration.

Teleporting back through the Gateway and switching game modes don't fix the problem, however dying or teleporting to the Overworld do.