The confusion is that my particular router has updated (2016) binaries on the ftp mirror but old (2013) ones on the secure portal.. Also I didn't see Hashes or checksums on either. I do see the hashes page: https://www.dd-wrt.com/wiki/index.php/Hashes_%26_Checksums
But that doesn't seem to have my router model/binary listed.
I believe you have already known the answer, ftp has updated build and secure portal has old ones. There are no Hashes or Checksums as they are not provided.