If you’re setting an app to be your default browser or email client, you probably trust it with your data. However, you still have to manually grant it permission for everything. Starting with Android Q, apps set as defaults will be automatically granted permissions based on what they are the default for.
Android Q introduces a new function called ‘Roles’, which “allows the OS to grant apps elevated access to system functions based on well-understood use cases”.
I’m not entirely sure this is a great idea. I can easily see scammers trying to trick people into setting a malware app as default, granting it easier access to their device.