Currently EncFSFile.copy() takes a different code path if the volume is using uniqueIV - this is not necessary. Unique IV header is generated randomly and is not dependent on the file path (unless external IV chaining is enabled - which is not supported yet), so there is no reason not to use fileProvider.copy (which is more efficient for most file providers) instead of doing a full stream read/write copy.
Currently EncFSFile.copy() takes a different code path if the volume is using uniqueIV - this is not necessary. Unique IV header is generated randomly and is not dependent on the file path (unless external IV chaining is enabled - which is not supported yet), so there is no reason not to use fileProvider.copy (which is more efficient for most file providers) instead of doing a full stream read/write copy.