as style have prgressed they have become more spcialised in their fields, be it striking, grappling, practical self defense or sport. these specialisation have altered some techniques, created some teachniques and rendered some obsolite.
However we still have the kata/forms to record the original teachniques even if they are not used. if we look at the common movement found in other arts no matter what the origin can we then make the assumtion that those techniques can be found in traditional kata somewhere if we look hard enough.
For example, kotegashi (wrist lock turning the opponents hand to the outside of his body) is maybe most commonly seen in Aikido demosonstrations, but the same lock can be found in ju jitsu, eskrima, krav maga and so on. it stand to reason that such a common movement must be in the forms somewhere.
the same can be said for the cross buttocks throw that iain presents on this website.
are there any other movements that are so common in other styles that must be present in forms?