In fact I have now checked the official install guide at
http://docs.fedoraproject.org/install-guide/f10/en_US/sn-installing-from-...
and one sees that for the HD install the guide says "Also specify the
Directory holding images....":
Partition type Volume Original path to files Directory to use
VFAT, NTFS D:\ D:\Downloads\F10 Downloads/F10
ext2, ext3 /home /home/user1/F10 user1/F10
One can see that the official documentation in the latter case omits the
crucial "/" on the right hand side.
This needs to be amended in the official F10 install guide since the
released F10 isos cannot be changed at this stage.