I guess it could but each situation can be extremely different. With a knife use like you described, you are right next to the suspect and it can be a little harder to tell when the threat has stopped since a natural reaction would be for that suspect to grab you, whether for self defense, further attack or even just some instinctive reaction not even thought through. If you were to shoot the suspect, you are father away (usually at least out of arm's reach) and can usually tell if the suspect is stopping his/her assault or not. If a shooting investigation protocol is properly followed, all of those things are considered in making a determination of whether it was self defense or not.
As an example using a knife for a weapon, a guy in one of our towns heard his neighbor screaming. He looked over and saw that a nephew had stabbed his uncle with a knife and was closing on the uncle to stab him again. The guy had his CCW gun with him and ordered the nephew to stop. The nephew continued trying to stab his uncle and the guy shot him. The nephew was DOA, the uncle was actually grateful for having his life saved and the guy was cleared by a shooting investigation.