The cord is designed to get rid of an incorrectly opened main parachute. Not an unopened one. This is to allow safe deployment of the reserve parachute.

On modern parachutes it won't actually get rid of an unopened main parachute. A main parachute that refuses to open at all is actually scarier than a poorly opened one, because it could get open anytime. Including after you have opened the reserve one. Then you have two parachutes open, and they can get into surprising unstable aerodynamic configurations (a downplane). And you can't easily get rid of an unopened main parachute.

Source: I learned skydiving this summer

I don't know how it was in 1986, but today you have 3 "chords". One in the back is the primary chute and hopefully the only one you need. On the front you have two. One cuts the primary, whether or not you've opened it, and the other deploys the secondary.

Should the main chute be tangled and you want to deploy a reserve probably