The keyboard accesses written media in order to write to it. In other words, it needs to access an email in order to respond to it. That's different to access to your account.
Let's look at it from the perspective of a photo app. It needs access to your photos in order to be able to edit them. Otherwise it couldn't perform itis functions. That's different than access to them in order to store them or to use them beyond the intended function.
I don't mind Photoshop Express accessing my photos. I don't, however, give those photos to a storage solution that I don't trust. And I don't give Photoshop Express the option of saving them for me. My photos are in my device, my laptop, and in iCloud.
Hope that explains it a bit.