Even if the instructor doesn't have the goods to deliver in terms of IP/IS, what if they're teaching Chansi Jin or Chansi Gong form? Would not knowing the basic form be something that could be played with after working with you or Sam or others with the goods to start developing IP/IS?
I'd expect Dan or Sam to show the exercises you need to develop IP/IS. So why put time in learning some other form?
Secondly, who says that the specific IP/IS mechanics as taught by Dan or Sam are a perfect match with the mechanics of Chansi Jin or Chansi Gong?