Google isn't exactly excited about the concept of local files. They would prefer you to keep everything in their online services.
If you need support for these, then installing a separate file manager app is your best bet.
I'm using this one:
https://f-droid.org/packages/me.zhanghai.android.files/
(No idea, though, if it supports unpacking RAR archives.)
Agile tries to solve this differently.
First and foremost, it puts you into tight-knit communication with your team and the customers, so just ask if anyone remembers why it is like that.
If no one does, then Agile enables to basically fuck around and find out.
Which is to say, change it to how you think it's supposed to be and see if anything breaks / anyone complains. If that happens, Agile allows you to react quickly, i.e. to change it back and quickly release a fixed version.
But yeah, as the others said, if your team feels like documents work better for them, then do Agile and documents. That's why retrospectives are an integral part of Agile, because it's not a perfect plan how to work together. You'll know best what works in your context.