The process of building custom applications and tools that interact with Microsoft Exchange Server
Well, those are all delegated perms. so in that case, it would allow the user to access mailboxes they all ready have access to.
You would generally use "Application" perms and then in that case, you can limit the mailbox access the app has using an access policy
https://learn.microsoft.com/en-us/graph/auth-limit-mailbox-access