While this does not answer your question per se you can use the track option to eliminate the duplicate check.
In other words, the SSL backend can track the checks done by the non-SSL
backend.
backend nginx-ssl
mode tcp
balance leastconn
server app1 app1.prod:444 track nginx/app1
server app2 app2.prod:444 track nginx/app2
server down localhost:81 backup

