RadUplaod and RadAsync upload are not depending from the OS, used by the user. He/she can upload each file from the used device, that he/she has permissions to.
If you want, though, to be able to directly list files from the client iOS device - I am afraid that this cannot be done neither with nor without a custom content provider.
If non of the above is the case - could you explain in more details what is the exact scenario you want to achieve?
Looking forward to hearing from you,
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