I did sign in as admin. However, I copied these files under an AD user ID from another ReadyNAS nv share. They inherited Windows ACL and admin was not part of that. Anyway, I found another way to test the timestamp and I am happy to report back that using your web-based editor, the timestamp has been updated correctly in all three cases (file size decreased, file size remained the same and file size increased). Even the archive bit has been set.
Unfortunately, the web base interface is not a work around for us as this is intended to supplement Windows shares under Windows Explorer.