I think what may be happening is after the upgrade to 11, the OS boots and attempts to find all the hardware it is expecting and loads the appropriate drivers or kexts for that hardware. When a third party screens controller isn't the same that is used by Apple is detected, it doesn't load that driver. So the touch never works. This would make sense because a fix I'm seeing around the internet that works is to install the original screen with the Apple controller, upgrade to 11, let it load the touchscreen driver, then swap screens. Since the driver had already been picked before hand, it just works with the new screens controller. I might be wrong about this, but it seems like a change Apple made in os 11.