This imperfection feeds into the argument for not punishing rape as harshly as murder: the rapist is likely to misjudge the chances of the murder being discovered and traced back to them, when doing the risk math to decide how to proceed. If their imperfect thinking leads them to overestimate their chance of pulling off the perfect murder (or the perfect coverup after one) then that pushes the chance of equal punishment leading to more murders higher.

"Doing risk math" oversells it for crimes of opportunity, where decisions about how to keep the action quiet after it has happened is going to be very emotion/panic (rather than facts/stats) driven, but for premeditated attacks I suspect things will flip the other way.