So Whatsapp tells other participants in a call what your battery life is? By itself, I suppose that's pretty harmless. But it's really none of your business what the status of my phone is in general.
I guess I don't really want an app doing that given it could probably tell participants other things that I don't want them to know, especially if I enabled something like location services.
Permission controls are a bandaid as someone else wrote.
Let's use the location services example.
So some communications app asks me for permission. Do I grant it? Well, as an unsophisticated user, maybe it wants this info to optimize the quality of my connection in some way. So maybe I ought to give it permission?
Instead, maybe it's going to broadcast my coordinates to everyone else on the call which is not OK in general.