Within this version of 1.17, the entity a part of the fishing rod, "fishing hook" (in codebase "fishing_hook") when using the command /kill gives off any item applies to all fishing loot. So even with enchantments on, it does build more luck within the loot table for fishing.
How to replicate:
1. Use any command block (since you want this to be repeated without use commands within the chat
2. Input this command: /kill @e[type=fishing_hook]
3. Recommended: Use Ticking Delay to delay the command every repeated cycle to see more of the issue
At this point, you should see items dropping from the hook. This is possibly due to the fishing hook registering that when you kill the hook, it detects that you're reeling in the actual item from the fishing reel when the rod is detected to have a "fish" nearby (or a catch in general). It never happened or occurred within the previous version.
I discovered this while being in the world that I mentioned earlier, but I was testing out something within a save and just discovered this when using a fishing rod (in which the rod was going to be used as a weapon for a map).