I found out about this when I was showing off in a realm while flying with my elytra when it was raining. I know for a fact that it's a bug because the player is supposed to swing back it's hand before thrusting forward.

What I expected to happen was:
The player's hand would slowly swing backwards before using riptide.

What actually happened was:
Nothing.

Steps to Reproduce:
1. Have a Trident enchanted with Riptide of any level.
1.5. Wait for Rain/Thunder to occur if no cheats are enabled. If cheats are enabled enter the following command:
/weather rain.
2. Have Third Person Front view enabled.
3. Attempt to use the Trident w/ Riptide. (Careful where you use it if in survival)
4. Observe to see if your hand swings backwards.

Files:
https://drive.google.com/file/d/1nAbvxIRQ-GGjSK5KU9D2ZUzxvLqESwdz/view?usp=sharing
https://drive.google.com/file/d/1cOvkfx31HHdZn5ZwoHceDt68ewLQtiDd/view?usp=sharing