I was able to patch nginx-1.9.10 which supports both SPDY + HTTP2. I don't intend to use both of them simultaneously on the same interface.

My question: Is there a reason why this is not done? It gives me an option to choose between the two per interface.

server {
listen x.x.x.x:443 ssl http2;
server_name abc.com;
...
}
server {
listen y.y.y.y:443 ssl spdy;
server_name def.com;
...
}