I think they've been wanting to get this patch into OpenSSH for years, but for whatever reasons it just never happened. I assumed it was a community patch, but it was actually written by Darren Tucker, who is an OpenSSH dev.

There was some conversation about if it was appropriate to pass on certain signals, but that's about it. After Darren cleaned up some client UI issues that bugged him, he even suggested that we might see the patch in 5.4.