This likely happened after enchantments were changed to be editable through datapacks, and the game added a check to see where the item is in your slot. Riptide is the only enchantment in vanilla that is supposed to work both in your mainhand and off hand, but due to an oversight, that also means having two tridents, one in each hand, stacks the effect.

In 1.20.6, this bug also happens, but you only get the animation playing for both arms. You don't get the triple distance. Only in the latest snapshot, at the time 24w20a, do you also get triple distance.

Discovered this bug after watching https://youtu.be/Nh0hvldZr5c?si=hAOiEZYIj01ryc3V. The video creator proposed a fix by changing the riptide enchantment to set a certain distance rather than add, but that doesn't address the animation error.