These are the justifications of developers who are unfamiliar with the Intent system. Were I unaware of Intent, I would make the same design decisions.
https://developer.android.com/training/contacts-provider/mod...
https://developer.android.com/guide/topics/providers/calenda...
and so on and so forth for almost any permission the Signal app needs on Android.
What if I never want to share my location, take pictures, or send files?
And then some things, like calendar access, aren't even used right now.
Don't use these features and / or disable the corresponding permissions.
If I'm about to take a picture for the first time using it then I'll understand it asking for camera access.
This provides more choice, and reduces the amount of needed permissions.