Given that --export --export-options export-minimal,export-clean does not include unusuable User IDs, it seems odd that it includes unusable subkeys (i.e. subkeys that are revoked or expired).
0 dkg@alice:~$ gpg --list-keys $PGPID
gpg: please do a --check-trustdb
pub rsa4096 2007-06-02 [SC] [expires: 2018-12-31]
0EE5BE979282D80B9F7540F1CCD2ED94D21739E9
uid [ultimate] Daniel Kahn Gillmor <dkg@fifthhorseman.net>
uid [ultimate] Daniel Kahn Gillmor <dkg@openflows.com>
uid [ultimate] [jpeg image of size 3515]
uid [ultimate] Daniel Kahn Gillmor <dkg@debian.org>
uid [ultimate] Daniel Kahn Gillmor <dkg@aclu.org>
sub rsa4096 2017-12-04 [E] [expires: 2018-12-31]
sub rsa4096 2017-12-04 [S] [expires: 2018-12-31]
sub rsa3072 2017-12-04 [A] [expires: 2018-12-31]
0 dkg@alice:~$ gpg --export-options export-minimal,export-clean --export $PGPID | gpg --list-packets | grep -c 'sub key'
13
0 dkg@alice:~$I think that either (or both) of export-minimal or export-clean should also mean dropping unusable subkeys.
At a minimum, there should be an option to explicitly exclude them from export.
(yes, i have several unusable subkeys, because i practice regular subkey rotation)