Hello Marlon,
Just my two cents, but I believe that many versions of SK techniques are taught for a particular type of attack even if it is simply a high punch versus the low punch. Often they are taught from right straight punch to chest. From a teaching point of view it is much easier to learn techniques all from one attack otherwise you have to memorize the attack as well as the defense.
I.E. DM(Combination)5 - Often taught as Box step left knife hand block with right driving chicken directly below. Right circular backfist to the nose. Right side thrust kick to solar plexus or ribs depending on how they are standing.
USSD states this as a modified knife technique in their manual. To apply it against a straight knife the initial block becomes rising chicken wrist and dropping knife hand to the wrist(slightly offset, if you can break their wrist than you can probably break your own if line the strikes up and you miss). This is supposed to drop the knife. Instead of just backfisting on the next move you also perform grab the opponents wrist if they still have the knife this will help control them, but personnally the side kick is going to the knee at that point as I am not going see if my grip is tight enough to keep the knife from pulling between my hands.
At first glance for a beginner student they may ask why do we this crazy chicken wrist knife hand block thingy at the beginning of the straight punch version of #5. Possible answer, it's closer to the knife technique they want you to eventually have as DM #5. It works against a straight punch, but it looks funny and always gets the question why not use a simpler block.
I think that DM #5 stands out to many people, because USSD does list it as having a knife alternative in the manual, but I don't think it is the only one. I would suspect there are many if not all.