Collecting new fairies in Hyrule Warriors Legends

I recently started playing Hyrule Warriors Legends for the first time. When I first launched the game, it downloaded a bunch of updates and then bombarded me with a massive list of rewards that went with the updates (e.g. 6 million rupees, 6 fairies, tons of food, etc).

The game lets you collect fairies in the Adventure mode. Or at least, it's supposed to. However, when I collect a fairy in Adventure mode (by capturing the keep that holds the fairy, walking over the fairy, and getting a message that I've collected a new fairy), nothing happens at the end of the mission related to the fairy, and no new fairies are added to my inventory.

This wiki page says that you can only hold a maximum of 3 fairies, but that maximum can increase by completing Adventure Mode maps. Since I already have 6 fairies, I assume the maximum is at least 6. The page also says that when you collect a new fairy, the game will ask whether you want to get rid of a previous fairy. However, I've never seen such a dialog. I started the game with two water fairies and two light fairies, so I'd like to get rid of the duplicates, but can't figure out any way to dismiss fairies and don't seem to be given the opportunity after "collecting" new fairies.

Am I misunderstanding something about the fairy system? How come nothing happens when I collect a new fairy?

The fairies you get when freeing a fort are different from the ones you can use in battle.

Fairies that you capture when freeing a fort are only for freeing an elemental fort with the same element. You'll see a message "Fairy acquired! Rescued a fairy of {element}".

Fairies that you can keep, train and use in combat, on the other hand, can only be found on certain maps in Adventure Mode, where you'll see a small fairy icon as you go through the various rewards that the particular battle has in store for you.

These fairies are usually only found in pots that you can find in forts. You can usually find them in the bright yellow/beige pots, where you can also find rupees and food. When you capture these fairies, the message will specifically mention "MY FAIRY" and "Companion Fairy".

From these fairies you can have 6 at the beginning and unlock the possibility to have more by finishing more adventure maps.