Flex is built into a lot of composite components to achieve a desired feel. Look at golf club shafts, tennis racquets, skis, etc. My fork flexes front to back, but not side to side. During hard braking, I can see the legs get pushed back slightly. it seems to me that if the fork legs are flexing, then there's probably less stress on the crown, steerer, head tube and joints. Nothing to do with the era a component comes from.