The technique itself does not. It comes into play in terms of having additional leg strength, balance, and being less afraid of falling when learning to do other spin or jump kicks. Once people are able to hang long enough to do the actual scissor kick, a lot of the other kicks come easily when taught.How does the jump scissor kick come into play later?
Probably. You can learn those skills in a bunch of different ways. That happens to be the one that school uses, and I find it effective (if there's a desire to learn the other 'fancy' kicks), so I've not had a need to figure out alternatives. It's also fun for them.Is there another way you could teach it than the impractical technique?
I can only speak for the schools I've been in, but it depends, mostly on age, and which technique. Something like combination 14, it's told pretty much right off the bat what the purpose is, regardless of age. Combination 1 will be broken into different parts when taught and trained. For kids, it's just each part taught. Giving them too much info will likely confuse them, and it gives them the opportunity to discover as they're training later on.How is it explained to the students which techniques are directly applicable and which are building blocks for future techniques?
For teens or adults, the concepts and reasoning are taught as the technique is taught. When it comes to upper colored belts/black belts (which are exclusively teens to adults), none of the instructors I've had (or myself when I've taught), have hidden their own thoughts behind a technique.