Maybe Raptor knows something that we don't, but he needs to explain it in his post, not just take his opinion/theory and write it out as fact. The muscle spindles, which are responsible for activating the stretch shortening cycle, respond to both changes in muscle length AND the rate/speed of change in length. Regardless of how flexible you are statically, I would think it would still kick in during a rapid eccentric contraction. Like in a depth jump, your knees don't bend much to stretch the quadriceps, it's the rate/speed of that stretch that causes the reflex.