As a followup, the argument that the preferred hashes "weren't added" to GNUGPG until after 2009 is meaningless. Read RFC 4880:
https://tools.ietf.org/html/rfc4880#section-9That is the RFC from November 2007. Now look at section 9.4, the preferred hashes. Hash algorithms 1 through 11 are in there. They are not experimental, they are standard hashes.
GNUPGP was just one of a number of OpenPGP implementations. PGP itself dates back to 1991. OpenPGP to 1997. Looking at the preferred hash list is meaningless.