I play only locally, no server or cloud, and I have put my world files on 3 computers now, and everything always transfers fine.
your world is the 2 files, the db and fwl. The old files are the previous save as a backup.

you have done it right, so either you are not where he built, or they are not up to date. You can look at the windows timestamp on the original files (you may need your friend to look at this on HIS machine) to see if they are being updated.