Good point
Teach everything, when the student is ready they will mix and match bits of technique to fit the situation.
We look at set techniques as a way to introduce a student to the basic tools and their application. This lets the student perfect the use of their available weapons, learn about important stuff like safety, protection, targets, body position, application and follow up
Once a student becomes less mechanical we teach them to mix and match the tools to a level that they can hold their own in a fairly pressured random attack lineup. You don't have to get lumped too often to learn that you need to select appropriate responses and have a choice.
(We don't teach Kenpo but we still utilise the principles that we have learnt in the past)