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.
Were hash algorithms 1 through 11 added to any well known OpenPGP implementation before 2009?
I doubt Satoshi would use a key in an experimental OpenPGP implementation he had written himself to link his key to the Bitcoin project.
Any good programmer knows software needs testing by a community before it's got any bugs ironed out. All programmers are likely to miss some bugs, which is why beta testing by a community is important.
Why would Satoshi use his own untested beta software for something vitally important when he could use the same reliable software used by everyone else?