Yes, that is what I meant, I always had problems with it. Iirc Android uses the mtp protocol for file transfer, it is not like accessing external storage. Before I can read / write files to the phone's storage I have to perform some steps on the phone's UI (this already rules out doing this while the phone is off); the exact steps changed between android versions. And then if I manage to remember, not all files and directories are visible.

With a pocketbook, you connect it and it is like you attached a USB stick.