Part of that is handling the Discord overlay. So, when you are in a game, and you are in a Discord VC, you can display who is talking. There are keyboard shortcuts that come along with that which you can use if you want.
In order to detect those keyboard short cuts, they need to listen for them.
You are free to not give them permission.
Posting about asking permission under a comment talking about "abusive" behavior is a bit odd.
Opening a new tab telling you about changes in the ownership of a piece of software that has the ability to open tabs autonomously is not abusive. Moreover it is not even a problem with the extension, it is a problem with the opersting system it runs on.
Analogously, i am sure that discord would have preferred to have finer control over the permissions it requests, but Apple's mission is security theater. If apple exposed a set of "application specific out of focus keybinds". The security breach would not be necessary.
As it stands lots of software in the apple ecosystem has identical permissions to discord, but those don't get scary warnings associated to them. This constitutes a (clearly illegal) competitive advantage for Apple and they have no interest in removing this advantage by offering finer permissions controls, even in the case where they do not offer competing software.
In order to detect those keyboard short cuts, they need to listen for them.
You are free to not give them permission.
Posting about asking permission under a comment talking about "abusive" behavior is a bit odd.