Does Stretching Make You Weaker? Or....??

Dude, you have got this all twisted around and the effect you’re experiencing is with out a doubt a palecbo.
The so called Stretch Muscle Reflex is a fact. However it is not achieved by stretching, in fact, stretching inhibits the possibility to create a so called Stretch Muscle Reflex.
The reflex is engaged to protect the muscle from a rupture, which happens when you preform a quick motion that is too long for the muscle to handle. When you stretch for 15 sec, all you do is increase the lenght of the muscle slowly and makes the tendon “flappy”.
A metaphor could be a rubber band, when pulled and released it snapps back. But when pulled and kept for say, a week, it will not be snapping back, it will be flapping back =)
For example, a discus thrower uses the stretch reflex as he engages his last step, the throw. But he builds up the energy in his m. Pectoralis Major by increasing the length of it during the spin. The longer he can keep the upper body separated from the lower body the greater a force will he be able to put into the throw!