sftp for file transfers!

According to the man page (of the debian package at least), sftp is only used for file listing and deletion and scp is used for actual file transfers.
The verbose output, however, indicates that sftp is used for file transfer in a restore command:

...
State = sftp, Before = 'Connecting to ss1...'
sftp command: 'get <remote-file-full-path>.gpg <some-file-in-/tmp>'

(and I can see sftp running in my 'ps ax' output)

The reason for my question is that I'm using duplicity to backup to a SunOS server. Backups seem to work fine. But, for some reason, I can grab the gpg file from the server manually only with scp. sftp will always stall at 99%. The files produced by sftp and scp have the same size, but sftp's file will not untar (actually gpg -d will complain before that).

I discovered this discrepancy of scp and sftp behavior as a result of duplicity halting during a restore operation at the lines shown above. At that point, killing sftp reinvokes it over and over again, and Ctrl-c duplicity terminates the restore operation unsuccessfully.

So, my question again:
Why is duplicity actually using sftp to transfer files back from the backup server although the man page says scp should be used?
And is their a way to force using scp instead of sftp?