SSH generic socket forwarding for gpg-agent

[Daniel]

I got the forwarding working, gpg-connect-agent says "connection to agent is
in restricted mode" and gives me a prompt. So am I all set? Doesn't seem
like that.

My GPG_AGENT_INFO is empty, as it is on my local machine where everything
works as expected (once my gpg-agent is running, has a key, and has created
its ~/.gnupg/S.gpg-agent -- and yes, now it also creates S.gpg-agent-extra
which I forward to)

So, on remote, "gpg --use-agent test.asc" gives me "gpg: decryption failed:
No secret key". But shouldn't this just work? Shouldn't it just get the
private/secret key from the (forwarded) socket? I tried pointing
GPG_AGENT_INFO at that socket as well, to no avail.