nginx 1.15.3
nginx-rtmp-module 1.2.1

The wiki says exec_options is valid in rtmp, server, or application blocks, and it is indeed accepted in all of them, but only appears to have an effect in an application block.

rtmp {
    exec_options on;
    server {
        listen 1935;
        application live {
            live on;
            exec_push ffmpeg -i foo bar name=mystream;
        }
    }
}

Expected: exec_options on; applies to all servers and applications where it's not overridden
Observed: exec_options on; is not observed (ffmpeg is run for all stream names), and name=mystream is put into the ffmpeg arguments.

Workaround: Add exec_options on; to each application block