Don't know what you're talking since I have no idea what nomenclature means, sorry, my English isn't as good as it should be (try learning another language while taking hits to your brain and then study German afterwards).
Anyway, to most people lead straight and jab looks exactly the same and people think it's a jab, but there's a difference. The lead straight is a mix between the cross and the jab, done with the lead hand.
The jab, is a snappy punch done in conjunction with a step forward of the lead leg. It's very snappy like a whip, so the whiplash effect is the main power of it.
The straight lead, is a follow-through type of punch. It's done by stepping forward with the lead leg, rotation of the upper body to add momentum, and rotation of the hip to add power, and the punch is throw forward with power, which is aimed "through" the target. Usually this punch is done if you're really good with slipping by rotating your upper body and head.
Done with speed, it looks exactly like a jab to most people, even martial artists, that's why some boxing organizations didn't recognize it as a technique. Bruce Lee recognized it, many Cuban and Central American nation also does.
If you're good at slipping by rotating your upper body, this is a very good technique but some times people prefer to deliver body or head hooks from the slip, so figures.