Don't take this wrong and I hate to be "that guy", but this is a terrible analogy.
With a skydiver, they're manually cutting away their primary chute in order to deploy a reserve chute. With saddle hunting, what is your reserve that you're cutting your primary towards?
If people are truly hung up on bring something for the "what if", bring trauma shears, not a knife. Trauma shears will cut through webbing, clothing, gloves, hair, etc. that may get sucked up into a belay device but won't cut through your main line. If your only option is to cut your main line without a proper backup under load, reevaluate your position and try again.