The 1.17 Pre-release 1 Article on minecraft.net has the following information under the using_item advancement trigger info:

Triggered for every tick of using items (like crossbows, spyglass, fishing rods, etc)

However, fishing rods do not actually work with this trigger in-game.

This could be a typo in the article, or rather a bug in the actual game.

Steps to reproduce:

1. Place the attached data pack into your world. This pack triggers a tellraw command when the using_item trigger is triggered.
2. Use a spyglass
   -> The message appears
3. Use a fishing rod
   -> No message appears